docs: refine plugin documentation (#2053)

packages/docs/docs/plugin/README.md

 # Plugin
 
-Plugins generally add global-level functionality to VuePress. There is no strictly defined scope for a plugin - there are typically several types of plugins:
+Plugins generally add global-level functionality to VuePress. There is no strictly defined scope for a plugin. You can find out more plugins at [Awesome VuePress](https://github.com/vuepressjs/awesome-vuepress#plugins).
+
+## Examples
+
+There are typically several types of plugins:
 
 1. Extend the page’s metadata generated at compile time. For example [@vuepress/plugin-last-updated](./official/plugin-last-updated.md);
 2. Generate extra files before or after compilation. For example [@vuepress/plugin-pwa](./official/plugin-pwa.md);
@@ -9,6 +13,25 @@ Plugins generally add global-level functionality to VuePress. There is no strict
 
 Here is also a little slightly complicated plugin example [@vuepress/plugin-blog](https://vuepress-plugin-blog.ulivz.com) that uses compile-time metadata to generate some dynamic modules and initialize them on the client-side by using `enhanceAppFiles`.
 
+## Out of the Box
+
+To keep things at a minimum, not all of the official plugins are shipped with VuePress. Here is the list of plugins that are pre-installed in the VuePress and the default theme, **plugins that are not in the list below need to be installed manually**(e.g. [@vuepress/plugin-back-to-top](./official/plugin-back-to-top.md)).
+
+### Plugins that come with VuePress
+
+- [@vuepress/plugin-last-updated](./official/plugin-last-updated.md)
+- [@vuepress/plugin-register-components](./official/plugin-register-components.md)
+
+### Plugins that come with the defualt theme
+
+- [@vuepress/plugin-active-header-links](./official/plugin-active-header-links.md)
+- [@vuepress/plugin-nprogress](./official/plugin-nprogress.md)
+- [@vuepress/plugin-search](./official/plugin-search.md)
+- [vuepress-plugin-container](https://vuepress.github.io/plugins/container/)
+- [vuepress-plugin-smooth-scroll](https://vuepress.github.io/plugins/smooth-scroll/)
+
+## Architecture
+
 The architecture of the whole plugin system is as follows:
 
 ![Architecture of VuePress](/architecture.png)

packages/docs/docs/plugin/official/plugin-active-header-links.md

@@ -23,12 +23,12 @@ module.exports = {
 ```
 
 ### Passing Options
+
 ```javascript
 module.exports = {
   plugins: ['@vuepress/active-header-links', {
     sidebarLinkSelector: '.sidebar-link',
-    headerAnchorSelector: '.header-anchor',
-    headerTopOffset: 120
+    headerAnchorSelector: '.header-anchor'
   }]
 }
 ```
@@ -44,4 +44,3 @@ module.exports = {
 
 - Type: `string`
 - Default: `.header-anchor`
-

packages/docs/docs/zh/plugin/README.md

 # 插件
 
-插件通常会为 VuePress 添加全局功能。插件的范围没有限制——一般有下面几种：
+插件通常会为 VuePress 添加全局功能。插件的范围没有限制。你可以在 [Awesome VuePress](https://github.com/vuepressjs/awesome-vuepress#plugins) 中找到更多的插件。
+
+## 样例
+
+以下是几种比较常见的插件：
 
 1. 拓展在编译期生成的页面元数据，如：[@vuepress/plugin-last-updated](./official/plugin-last-updated.md)；
 2. 在编译前后生成额外的文件，如：[@vuepress/plugin-pwa](./official/plugin-pwa.md)；
 3. 注入全局的 UI, 如：[@vuepress/plugin-back-to-top](./official/plugin-back-to-top.md);
-4. 拓展 CLI 的指令，如 [vuepress-plugin-export](https://github.com/ulivz/vuepress-plugin-export)。
+4. 拓展 CLI 的指令，如：[vuepress-plugin-export](https://github.com/ulivz/vuepress-plugin-export)。
+
+这里也有一个略微复杂的插件案例 [@vuepress/plugin-blog](https://vuepress-plugin-blog.ulivz.com)，其使用了编译器的元数据来生成了一些动态模块，并在客户端使用 `enhanceAppFiles` 来初始化他们。
+
+## 开箱即用
+
+为了让项目尽可能地简洁，并非所有官方插件都会随着 VuePress 一同安装。以下是一些随着 VuePress 和默认主题一同安装的插件，**没有出现在下表中的插件需要手动安装**（比如：[@vuepress/plugin-back-to-top](./official/plugin-back-to-top.md)）。
+
+### VuePress 自带的插件
+
+- [@vuepress/plugin-last-updated](./official/plugin-last-updated.md)
+- [@vuepress/plugin-register-components](./official/plugin-register-components.md)
+
+### 默认主题自带的插件
+
+- [@vuepress/plugin-active-header-links](./official/plugin-active-header-links.md)
+- [@vuepress/plugin-nprogress](./official/plugin-nprogress.md)
+- [@vuepress/plugin-search](./official/plugin-search.md)
+- [vuepress-plugin-container](https://vuepress.github.io/zh/plugins/container/)
+- [vuepress-plugin-smooth-scroll](https://vuepress.github.io/zh/plugins/smooth-scroll/)
 
-这里也有一个略微复杂的插件案例 [@vuepress/plugin-blog](https://vuepress-plugin-blog.ulivz.com), 其使用了编译器的元数据来生成了一些动态模块，并在客户端使用 `enhanceAppFiles` 来初始化他们。
+## 架构
 
 整个插件系统的架构如下:
 

packages/docs/docs/zh/plugin/official/plugin-active-header-links.md

@@ -22,6 +22,17 @@ module.exports = {
 }
 ```
 
+### 配置选项
+
+```javascript
+module.exports = {
+  plugins: ['@vuepress/active-header-links', {
+    sidebarLinkSelector: '.sidebar-link',
+    headerAnchorSelector: '.header-anchor'
+  }]
+}
+```
+
 ## 选项
 
 ### sidebarLinkSelector

packages/docs/docs/zh/plugin/official/plugin-medium-zoom.md

@@ -16,8 +16,6 @@ yarn add -D @vuepress/plugin-medium-zoom
 
 ## 使用
 
-## Usage
-
 **简单使用**:
 
 ```javascript