docs: add plugin install command

Author: meteorlxy

docs/reference/plugin/active-header-links.md

@@ -6,6 +6,12 @@ This plugin will listen to page scroll event. When the page scrolls to a certain
 
 This plugin is mainly used to develop themes, and has been integrated into the default theme. You won't need to use it directly in most cases.
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-active-header-links@next
+```
+
 ## Options
 
 ### headerLinkSelector

docs/reference/plugin/back-to-top.md

@@ -6,6 +6,12 @@ This plugin will add a _back to top_ button to your site. The button will be dis
 
 This plugin has been integrated into the default theme.
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-back-to-top@next
+```
+
 ## Styles
 
 You can customize the style of the _back to top_ button via CSS variables:

docs/reference/plugin/container.md

@@ -8,6 +8,12 @@ This plugin simplifies the use of [markdown-it-container](https://github.com/mar
 
 The [Custom Containers](../default-theme/markdown.md#custom-containers) of default theme is powered by this plugin.
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-container@next
+```
+
 ## Container Syntax
 
 ```md

docs/reference/plugin/debug.md

@@ -3,3 +3,9 @@
 <NpmBadge package="@vuepress/plugin-debug" />
 
 This plugin will add a debug component to your site. The component will only take effect in development mode.
+
+## Install
+
+```bash
+npm i -D @vuepress/plugin-debug@next
+```

docs/reference/plugin/docsearch.md

@@ -10,6 +10,12 @@ Default theme will add DocSearch to the navbar once you configure this plugin co
 This plugin may not be used directly in other themes, so you'd better refer to the documentation of your theme for more details.
 :::
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-docsearch@next
+```
+
 ## Get Search Index
 
 You need to [submit the URL of your site](https://docsearch.algolia.com/apply/) to join the DocSearch program. The DocSearch team will send [apiKey](#apikey) and [indexName](#indexname) to your email once the index is generated. Then you can configure this plugin to enable DocSearch in VuePress.

docs/reference/plugin/git.md

@@ -8,6 +8,12 @@ The [lastUpdated](../default-theme/config.md#lastupdated) and [contributors](../
 
 This plugin is mainly used to develop themes. You won't need to use it directly in most cases.
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-git@next
+```
+
 ## Git Repository
 
 This plugin requires your project to be inside a [Git Repository](https://git-scm.com/book/en/Git-Basics-Getting-a-Git-Repository), so that it can collect information from the commit history.

docs/reference/plugin/google-analytics.md

@@ -6,6 +6,12 @@ Integrate [Google Analytics](https://analytics.google.com/) into VuePress.
 
 This plugin will import [gtag.js](https://developers.google.com/analytics/devguides/collection/gtagjs) for [Google Analytics 4](https://support.google.com/analytics/answer/10089681).
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-google-analytics@next
+```
+
 ## Reporting Events
 
 Google Analytics will [automatically collect some events](https://support.google.com/analytics/answer/9234069), such as `page_view`, `first_visit`, etc.

docs/reference/plugin/medium-zoom.md

@@ -6,6 +6,12 @@ Integrate [medium-zoom](https://github.com/francoischalifour/medium-zoom#readme)
 
 This plugin has been integrated into the default theme.
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-medium-zoom@next
+```
+
 ## Options
 
 ### selector

docs/reference/plugin/nprogress.md

@@ -14,6 +14,12 @@ Integrate [nprogress](https://github.com/rstacruz/nprogress) into VuePress, whic
 
 This plugin has been integrated into the default theme.
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-nprogress@next
+```
+
 ## Styles
 
 You can customize the style of the progress bar via CSS variables:

docs/reference/plugin/palette.md

@@ -8,6 +8,12 @@ This plugin is mainly used to develop themes, and has been integrated into the d
 
 For theme authors, this plugin will help you to provide styles customization for users.
 
+## Install
+
+```bash
+npm i -D @vuepress/plugin-palette@next
+```
+
 ## Palette and Style
 
 This plugin will provide a `@vuepress/plugin-palette/palette` (palette file) and a `@vuepress/plugin-palette/style` (style file) to be imported in your theme styles.