copy Astro example from vercel/vercel (#1001)

### Description

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### Demo URL

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### Type of Change

- [ ] New Example
- [ ] Example updates (Bug fixes, new features, etc.)
- [ ] Other (changes to the codebase, but not to examples)

### New Example Checklist

- [ ] 🛫 `npm run new-example` was used to create the example
- [ ] 📚 The template wasn't used but I carefuly read the [Adding a new
example](https://github.com/vercel/examples#adding-a-new-example) steps
and implemented them in the example
- [ ] 📱 Is it responsive? Are mobile and tablets considered?

framework-boilerplates/astro/.gitignore

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+# astro
+.astro
+
+# build output
+dist/
+.output/
+
+# dependencies
+node_modules/
+
+# logs
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+
+# environment variables
+.env
+.env.production
+
+# macOS-specific files
+.DS_Store
+.vercel

framework-boilerplates/astro/.npmrc

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+# Expose Astro dependencies for `pnpm` users
+shamefully-hoist=true

framework-boilerplates/astro/README.md

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+# Astro
+
+This directory is a brief example of an [Astro](https://astro.build/) site that can be deployed to Vercel with zero configuration. This demo showcases:
+
+- `/` - A static page (pre-rendered)
+- `/ssr` - A page that uses server-side rendering (through [Vercel Functions](https://vercel.com/docs/functions))
+- `/ssr-with-swr-caching` - Similar to the previous page, but also caches the response on the [Vercel Edge Network](https://vercel.com/docs/edge-network/overview) using `cache-control` headers
+- `/image` - Astro [Asset](https://docs.astro.build/en/guides/images/) using Vercel [Image Optimization](https://vercel.com/docs/image-optimization)
+
+Learn more about [Astro on Vercel](https://vercel.com/docs/frameworks/astro).
+
+## Deploy Your Own
+
+Deploy your own Astro project with Vercel.
+
+[![Deploy with Vercel](https://vercel.com/button)](https://vercel.com/new/clone?repository-url=https://github.com/vercel/examples/tree/main/framework-boilerplates/astro&template=astro)
+
+_Live Example: https://astro-template.vercel.app_
+
+## Project Structure
+
+Astro looks for `.astro`, `.md`, or `.js` files in the `src/pages/` directory. Each page is exposed as a route based on its file name.
+
+There's nothing special about `src/components/`, but that's where we like to put any Astro/React/Vue/Svelte/Preact components or layouts.
+
+Any static assets, like images, can be placed in the `public/` directory.
+
+## Commands
+
+All commands are run from the root of the project, from a terminal:
+
+| Command                | Action                                             |
+| :--------------------- | :------------------------------------------------- |
+| `pnpm install`          | Installs dependencies                              |
+| `pnpm run dev`          | Starts local dev server at `localhost:3000`        |
+| `pnpm run build`        | Build your production site to `./dist/`            |
+| `pnpm run preview`      | Preview your build locally, before deploying       |
+| `pnpm run start`       | Starts a production dev server at  `localhost:3000`     |
+| `pnpm run astro ...`    | Run CLI commands like `astro add`, `astro preview` |
+| `pnpm run astro --help` | Get help using the Astro CLI                       |

framework-boilerplates/astro/astro.config.ts

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+import { defineConfig } from 'astro/config';
+import vercel from '@astrojs/vercel';
+
+export default defineConfig({
+  output: 'server',
+  adapter: vercel({
+    imageService: true,
+    webAnalytics: {
+      enabled: true,
+    },
+  }),
+});

framework-boilerplates/astro/package.json

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+{
+  "private": true,
+  "scripts": {
+    "dev": "astro dev",
+    "start": "astro dev",
+    "build": "astro build",
+    "preview": "astro preview",
+    "astro": "astro"
+  },
+  "dependencies": {
+    "@astrojs/vercel": "8.0.1",
+    "astro": "^5.1.1",
+    "react": "18.3.1"
+  }
+}

framework-boilerplates/astro/src/components/Card.astro

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+---
+export interface Props {
+	title: string;
+	body: string;
+	href: string;
+}
+
+const { href, title, body } = Astro.props as Props;
+---
+
+<li class="link-card">
+	<a href={href}>
+		<h2>
+			{title}
+			<span>&rarr;</span>
+		</h2>
+		<p>
+			{body}
+		</p>
+	</a>
+</li>
+<style>
+	:root {
+		--link-gradient: linear-gradient(45deg, #4f39fa, #da62c4 30%, var(--color-border) 60%);
+	}
+
+	.link-card {
+		list-style: none;
+		display: flex;
+		padding: 0.15rem;
+		background-image: var(--link-gradient);
+		background-size: 400%;
+		border-radius: 0.5rem;
+		background-position: 100%;
+		transition: background-position 0.6s cubic-bezier(0.22, 1, 0.36, 1);
+	}
+
+	.link-card > a {
+		width: 100%;
+		text-decoration: none;
+		line-height: 1.4;
+		padding: 1em 1.3em;
+		border-radius: 0.35rem;
+		color: var(--text-color);
+		background-color: white;
+		opacity: 0.8;
+	}
+
+	h2 {
+		margin: 0;
+		transition: color 0.6s cubic-bezier(0.22, 1, 0.36, 1);
+	}
+
+	p {
+		margin-top: 0.75rem;
+		margin-bottom: 0;
+	}
+
+	h2 span {
+		display: inline-block;
+		transition: transform 0.3s cubic-bezier(0.22, 1, 0.36, 1);
+	}
+
+	.link-card:is(:hover, :focus-within) {
+		background-position: 0;
+	}
+
+	.link-card:is(:hover, :focus-within) h2 {
+		color: #4f39fa;
+	}
+
+	.link-card:is(:hover, :focus-within) h2 span {
+		will-change: transform;
+		transform: translateX(2px);
+	}
+</style>

framework-boilerplates/astro/src/env.d.ts

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+/// <reference types="astro/client-image" />
+
+interface ImportMetaEnv {
+	readonly PUBLIC_VERCEL_ANALYTICS_ID: string;
+}
+
+interface ImportMeta {
+	readonly env: ImportMetaEnv;
+}

framework-boilerplates/astro/src/layouts/Layout.astro

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+---
+export interface Props {
+	title: string;
+}
+
+const { title } = Astro.props as Props;
+---
+
+<!DOCTYPE html>
+<html lang="en">
+	<head>
+		<meta charset="UTF-8" />
+		<meta name="viewport" content="width=device-width" />
+		<link rel="icon" type="image/x-icon" href="/favicon.ico" />
+		<meta name="generator" content={Astro.generator} />
+		<title>{title}</title>
+	</head>
+	<body>
+		<slot />
+	</body>
+</html>
+<style>
+	:root {
+		--font-size-base: clamp(1rem, 0.34vw + 0.91rem, 1.19rem);
+		--font-size-lg: clamp(1.2rem, 0.7vw + 1.2rem, 1.5rem);
+		--font-size-xl: clamp(2.44rem, 2.38vw + 1.85rem, 3.75rem);
+
+		--color-text: hsl(12, 5%, 4%);
+		--color-bg: hsl(10, 21%, 95%);
+		--color-border: hsl(17, 24%, 90%);
+	}
+
+	html {
+		font-family: system-ui, sans-serif;
+		font-size: var(--font-size-base);
+		color: var(--color-text);
+		background-color: var(--color-bg);
+	}
+
+	body {
+		margin: 0;
+	}
+
+	:global(h1) {
+		font-size: var(--font-size-xl);
+	}
+
+	:global(h2) {
+		font-size: var(--font-size-lg);
+	}
+
+	:global(code) {
+		font-family: Menlo, Monaco, Lucida Console, Liberation Mono, DejaVu Sans Mono,
+			Bitstream Vera Sans Mono, Courier New, monospace;
+	}
+</style>

framework-boilerplates/astro/src/pages/image.astro

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+---
+import { Image } from 'astro:assets';
+import astroLogo from '../assets/logo.png';
+---
+
+<Image src={astroLogo} alt="Astro Logo" width={50} quality={75} />

framework-boilerplates/astro/src/pages/index.astro

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+---
+import Layout from '../layouts/Layout.astro';
+import Card from '../components/Card.astro';
+
+export const prerender = true;
+---
+
+<Layout title="Welcome to Astro.">
+	<main>
+		<h1>Welcome to <span class="text-gradient">Astro</span></h1>
+		<p class="instructions">
+			Check out the <code>src/pages</code> directory to get started.<br />
+			<strong>Code Challenge:</strong> Tweak the "Welcome to Astro" message above.
+		</p>
+		<ul role="list" class="link-card-grid">
+			<Card
+				href="https://docs.astro.build/"
+				title="Documentation"
+				body="Learn how Astro works and explore the official API docs."
+			/>
+			<Card
+				href="https://astro.build/integrations/"
+				title="Integrations"
+				body="Supercharge your project with new frameworks and libraries."
+			/>
+			<Card
+				href="https://astro.build/themes/"
+				title="Themes"
+				body="Explore a galaxy of community-built starter themes."
+			/>
+			<Card
+				href="https://astro.build/chat/"
+				title="Chat"
+				body="Come say hi to our amazing Discord community. ❤️"
+			/>
+		</ul>
+	</main>
+</Layout>
+
+<style>
+	:root {
+		--astro-gradient: linear-gradient(0deg, #4f39fa, #da62c4);
+	}
+
+	h1 {
+		margin: 2rem 0;
+	}
+
+	main {
+		margin: auto;
+		padding: 1em;
+		max-width: 60ch;
+	}
+
+	.text-gradient {
+		font-weight: 900;
+		background-image: var(--astro-gradient);
+		-webkit-background-clip: text;
+		-webkit-text-fill-color: transparent;
+		background-size: 100% 200%;
+		background-position-y: 100%;
+		border-radius: 0.4rem;
+		animation: pulse 4s ease-in-out infinite;
+	}
+
+	@keyframes pulse {
+		0%,
+		100% {
+			background-position-y: 0%;
+		}
+		50% {
+			background-position-y: 80%;
+		}
+	}
+
+	.instructions {
+		line-height: 1.6;
+		margin: 1rem 0;
+		background: #4f39fa;
+		padding: 1rem;
+		border-radius: 0.4rem;
+		color: var(--color-bg);
+	}
+
+	.instructions code {
+		font-size: 0.875em;
+		border: 0.1em solid var(--color-border);
+		border-radius: 4px;
+		padding: 0.15em 0.25em;
+	}
+
+	.link-card-grid {
+		display: grid;
+		grid-template-columns: repeat(auto-fit, minmax(24ch, 1fr));
+		gap: 1rem;
+		padding: 0;
+	}
+</style>

framework-boilerplates/astro/src/pages/ssr-with-swr-caching.astro

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+---
+Astro.response.headers.set('Cache-Control', 's-maxage=10, stale-while-revalidate');
+
+const time = new Date().toLocaleTimeString();
+---
+
+<h1>{time}</h1>

framework-boilerplates/astro/src/pages/ssr.astro

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+---
+const time = new Date().toLocaleTimeString();
+---
+
+<h1>{time}</h1>