docs: official blog plugin and theme (#2149)

packages/docs/docs/.vuepress/config.js

@@ -171,6 +171,7 @@ function getThemeSidebar (groupA, introductionA) {
         'writing-a-theme',
         'option-api',
         'default-theme-config',
+        'blog-theme',
         'inheritance'
       ]
     }

packages/docs/docs/plugin/official/plugin-blog.md

+---
+title: blog
+metaTitle: Blog plugin | VuePress
+---
+
+# [@vuepress/plugin-blog](https://github.com/vuepressjs/vuepress-plugin-blog)
+
+## Features
+
+- [**Classification**](https://vuepress-plugin-blog.ulivz.com/guide/getting-started.html#document-classifier):
+Powerful classification system lets you quickly classify your posts.
+- [**Pagination**](https://vuepress-plugin-blog.ulivz.com/guide/getting-started.html#pagination):
+Pagination runs through the entire plugin, and it has never been so simple.
+- [**Client APIs**](https://vuepress-plugin-blog.ulivz.com/client-api/): Simple client APIs make it easier for you to write a blog theme.
+
+## Install
+
+We strongly recommend that you read the [Getting Started](https://vuepress-plugin-blog.ulivz.com/guide/getting-started.html) section before using this plugin.
+
+```bash
+yarn add -D @vuepress/plugin-blog
+# OR npm install -D @vuepress/plugin-blog
+```
+
+## Usage
+
+```javascript
+module.exports = {
+  plugins: ['@vuepress/blog']
+}
+```
+
+Please head [documentation](https://vuepress-theme-blog.ulivz.com/) to see all available options.

packages/docs/docs/theme/blog-theme.md

+# Blog theme
+
+## Sites
+
+- [Documentation](https://vuepress-theme-blog.ulivz.com)
+- [Live Example](https://example.vuepress-theme-blog.ulivz.com/)
+- [Live Example - ULIVZ’s space](https://ulivz.com/)
+- [Live Example - Billyyyyy3320’s space](https://billyyyyy3320.com/)
+
+## Install
+
+```bash
+yarn add @vuepress/theme-blog -D
+# OR npm install @vuepress/theme-blog -D
+```
+## Usage
+
+```js
+// .vuepress/config.js
+module.exports = {
+  theme: '@vuepress/blog',
+  themeConfig: {
+    // Please head documentation to see the available options.
+  }
+}
+```

packages/docs/docs/zh/plugin/official/plugin-blog.md

+---
+title: blog
+metaTitle: 博客插件 | VuePress
+---
+
+# [@vuepress/plugin-blog](https://github.com/vuepressjs/vuepress-plugin-blog)
+
+## 功能
+
+- [**分类**](https://vuepress-plugin-blog.ulivz.com/guide/getting-started.html#document-classifier)：强大的分类系统让你快速将贴文分类。
+- [**分页**](https://vuepress-plugin-blog.ulivz.com/guide/getting-started.html#pagination)： 极其简单的开箱及用分页功能。
+- [**客戶端 API**](https://vuepress-plugin-blog.ulivz.com/client-api/): 透过客户端API轻松地写一个博客主题。
+
+## 安装
+
+在使用这个插件之前，我们强烈建议你先阅读 [Getting Started](https://vuepress-plugin-blog.ulivz.com/guide/getting-started.html)。
+
+```bash
+yarn add -D @vuepress/plugin-blog
+# OR npm install -D @vuepress/plugin-blog
+```
+
+## 使用
+
+```javascript
+module.exports = {
+  plugins: ['@vuepress/blog']
+}
+```
+
+参考 [文档](https://vuepress-theme-blog.ulivz.com/) 来查看所有可用的选项。

packages/docs/docs/zh/theme/blog-theme.md

+# 博客主题
+
+## 网站
+
+- [文檔](https://vuepress-theme-blog.ulivz.com)
+- [线上范例](https://example.vuepress-theme-blog.ulivz.com/)
+- [线上范例 - ULIVZ's space](https://ulivz.com/)
+- [线上范例 - Billyyyyy3320's space](https://billyyyyy3320.com/)
+
+## 安装
+
+```bash
+yarn add @vuepress/theme-blog -D
+# OR npm install @vuepress/theme-blog -D
+```
+## 使用
+
+```js
+// .vuepress/config.js
+module.exports = {
+  theme: '@vuepress/blog',
+  themeConfig: {
+    // 请参考文档来查看所有可用的选项。
+  }
+}
+```