feat: add sitemap and robots.txt for SEO optimization

- Introduced next-sitemap configuration for automatic sitemap generation.
- Created robots.txt to manage web crawler access.
- Added initial sitemap-0.xml and sitemap.xml files for structured URL indexing.

next-sitemap.config.js

@@ -0,0 +1,15 @@
+/** @type {import('next-sitemap').IConfig} */
+module.exports = {
+  siteUrl: process.env.SITE_URL || 'http://localhost:3000',
+  exclude: ['/next.svg', '/vercel.svg', '/favicon.ico'],
+  generateRobotsTxt: true,
+  generateIndexSitemap: false,
+  robotsTxtOptions: {
+    policies: [
+      {
+        userAgent: '*',
+        allow: '/',
+      },
+    ],
+  },
+};

public/robots.txt

@@ -0,0 +1,9 @@
+# *
+User-agent: *
+Allow: /
+
+# Host
+Host: https://shadcn-timeline.vercel.app
+
+# Sitemaps
+Sitemap: https://shadcn-timeline.vercel.app/sitemap.xml

public/sitemap-0.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:news="http://www.google.com/schemas/sitemap-news/0.9" xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:mobile="http://www.google.com/schemas/sitemap-mobile/1.0" xmlns:image="http://www.google.com/schemas/sitemap-image/1.1" xmlns:video="http://www.google.com/schemas/sitemap-video/1.1">
+<url><loc>https://shadcn-timeline.vercel.app</loc><lastmod>2025-01-03T16:53:05.059Z</lastmod><changefreq>daily</changefreq><priority>0.7</priority></url>
+</urlset>

public/sitemap.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+<sitemap><loc>https://shadcn-timeline.vercel.app/sitemap-0.xml</loc></sitemap>
+</sitemapindex>