docs: new content for new feautures

Author: yyx990803

Diff for: docs/guide/basic-config.md

@@ -17,6 +17,10 @@ If you've got the dev server running, you should see the page now has a header w
 
 Consult the [Config Reference](../config/) for a full list of options.
 
+::: tip Alternative Config Formats
+You can also use YAML (`.vuepress/config.yml`) or TOML (`.vuepress/config.toml`) formats for the configuration file.
+:::
+
 ## Theme Configuration
 
 A VuePress theme is responsible for all the layout and interactivity details of your site. VuePress ships with a default theme (you are looking at it right now) which is designed for technical documentation. It exposes a number of options that allow you to customize the navbar, sidebar and homepage, etc. For details, check out the [Default Theme Config](../default-theme-config/) page.
@@ -31,7 +35,8 @@ Since the VuePress app is a standard Vue app, you can apply app-level enhancemen
 export default ({
   Vue, // the version of Vue being used in the VuePress app
   options, // the options for the root Vue instance
-  router // the router instance for the app
+  router, // the router instance for the app
+  siteData // site metadata
 }) => {
   // ...apply enhancements to the app
 }

Diff for: docs/guide/custom-themes.md

@@ -70,15 +70,16 @@ The compiled content of the current `.md` file being rendered will be available
 </template>
 ```
 
-## Theme Level Enhancements
+## App Level Enhancements
 
-Themes can extend the Vue app that VuePress uses by exposing an `index.js` file at the root of the theme. The file should `export default` a hook function which will receive an object containing some app level values. You can use this hook to install additional Vue plugins, register global components, or add additional router hooks:
+Themes can enhance the Vue app that VuePress uses by exposing an `enhanceApp.js` file at the root of the theme. The file should `export default` a hook function which will receive an object containing some app level values. You can use this hook to install additional Vue plugins, register global components, or add additional router hooks:
 
 ``` js
 export default ({
   Vue, // the version of Vue being used in the VuePress app
   options, // the options for the root Vue instance
-  router // the router instance for the app
+  router, // the router instance for the app
+  siteData // site metadata
 }) => {
   // ...apply enhancements to the app
 }

Diff for: docs/guide/markdown.md

@@ -1,9 +1,3 @@
----
-meta:
-- name: keywords
-  content: static docs generator vue
----
-
 # Markdown Extensions
 
 ## Header Anchors
@@ -67,7 +61,7 @@ Given the following directory structure:
   - [vuejs.org](https://vuejs.org)
   - [VuePress on GitHub](https://github.com/vuejs/vuepress)
 
-## YAML Front Matter
+## Front Matter
 
 [YAML front matter](https://jekyllrb.com/docs/frontmatter/) is supported out of the box:
 
@@ -92,6 +86,30 @@ meta:
 ---
 ```
 
+### Alternative Front Matter Formats
+
+In addition, VuePress also supports JSON or [TOML](https://github.com/toml-lang/toml) front matter.
+
+JSON front matter needs to start and end in curly braces:
+
+```
+---
+{
+  "title": "Blogging Like a Hacker",
+  "lang": "en-US"
+}
+---
+```
+
+TOML front matter needs to be explicitly marked as TOML:
+
+```
+---toml
+title = "Blogging Like a Hacker"
+lang = "en-US"
+---
+```
+
 ## GitHub-Style Tables
 
 **Input**

Diff for: docs/zh/guide/basic-config.md

@@ -17,6 +17,9 @@ module.exports = {
 
 参见 [配置](../config/) 来查看所有可配置的选项。
 
+::: tip 其他配置格式
+你也可以使用 YAML (`.vuepress/config.yml`) 或是 TOML (`.vuepress/config.toml`) 格式的配置文件。
+:::
 
 ## 主题配置
 
@@ -33,7 +36,8 @@ module.exports = {
 export default ({
   Vue, // VuePress 正在使用的 Vue 构造函数
   options, // 附加到根实例的一些选项
-  router // 当前应用的路由实例
+  router, // 当前应用的路由实例
+  siteData // 站点元数据
 }) => {
   // ...做一些其他的应用级别的优化
 }

Diff for: docs/zh/guide/custom-themes.md

@@ -70,6 +70,21 @@ VuePress 使用单文件组件来构建自定义主题。想要开发一个自
 </template>
 ```
 
+## 应用配置
+
+自定义主题也可以通过主题根目录下的 `enhanceApp.js` 文件来对 VuePress 应用进行拓展配置。这个文件应当 `export default` 一个钩子函数，并接受一个包含了一些应用级别属性的对象作为参数。你可以使用这个钩子来安装一些附加的 Vue 插件、注册全局组件，或者增加额外的路由钩子等：
+
+```js
+export default ({
+  Vue, // VuePress 正在使用的 Vue 构造函数
+  options, // 附加到根实例的一些选项
+  router, // 当前应用的路由实例
+  siteData // 站点元数据
+}) => {
+  // ...做一些其他的应用级别的优化
+}
+```
+
 ## 使用来自 npm 的主题
 
 主题可以以 Vue 单文件组件的格式，并以 `vuepress-theme-xxx` 的名称发布到 npm 上。
@@ -84,3 +99,6 @@ module.exports = {
 
 VuePress 将会尝试去加载并使用位于 `node_modules/vuepress-theme-awesome/Layout.vue` 的主题组件。
 
+## 修改默认主题
+
+你可以使用 `vuepress eject [targetDir]` 这个命令来将默认主题的源码复制到 `.vuepress/theme` 文件夹下，从而可以对默认主题进行任意的修改。需要注意的是一旦 eject，即使升级 VuePress 你也无法再获得 VuePress 对默认主题的更新。

Diff for: docs/zh/guide/markdown.md

@@ -1,9 +1,3 @@
----
-meta:
-- name: keywords
-  content: static docs generator vue
----
-
 # Markdown 拓展
 
 ## Header Anchors
@@ -22,7 +16,7 @@ meta:
   - [vuejs.org](https://vuejs.org)
   - [VuePress on GitHub](https://github.com/vuejs/vuepress)
 
-## YAML Front Matter
+## Front Matter
 
 VuePress 提供了对 [YAML front matter](https://jekyllrb.com/docs/frontmatter/) 开箱即用的支持:
 
@@ -47,6 +41,30 @@ meta:
 ---
 ```
 
+### 其他格式的 Front Matter
+
+除了 YAML 之外，VuePress 也支持 JSON 或者 [TOML](https://github.com/toml-lang/toml) 格式的 front matter。
+
+JSON front matter 需要以花括号开头和结尾：
+
+```
+---
+{
+  "title": "Blogging Like a Hacker",
+  "lang": "en-US"
+}
+---
+```
+
+TOML front matter 需要显式地标注为 TOML：
+
+```
+---toml
+title = "Blogging Like a Hacker"
+lang = "en-US"
+---
+```
+
 ## GitHub 风格的表格
 
 **Input**