docs(theme-default): add frontmatter reference

Author: meteorlxy

docs/reference/default-theme/frontmatter.md

@@ -1,3 +1,252 @@
 # Frontmatter
 
-> TODO
+## Home Page
+
+Frontmatter in this section will only take effect in home pages.
+
+### home
+
+- Type: `boolean`
+
+- Details:
+
+  Specify whether the page is homepage or a normal page.
+
+  If you don't set this frontmatter or set it to `false`, the page would be a [normal page](#normal-page).
+
+- Example:
+
+  ```md
+  ---
+  home: true
+  ---
+  ```
+
+### heroImage
+
+- Type: `string`
+
+- Details:
+
+  Specify the url of the hero image.
+
+- Example:
+
+  ```md
+  ---
+  # public file path
+  heroImage: /hero.png
+  # url
+  heroImage: https://vuejs.org/images/logo.png
+  ---
+  ```
+
+- Also see:
+  - [Guide > Assets > Public Files](../../guide/assets.md#public-files)
+
+### heroAlt
+
+- Type: `string`
+
+- Details:
+
+  Specify the `alt` attribute of the hero image.
+
+  This will fallback to the [heroText](#heroText).
+
+### heroText
+
+- Type: `string | null`
+
+- Details:
+
+  Specify the the hero text.
+
+  This will fallback to the site [title](../config.md#title).
+
+  Set to `null` to disable hero text.
+
+### tagline
+
+- Type: `string | null`
+
+- Details:
+
+  Specify the the tagline.
+
+  This will fallback to the site [description](../config.md#description).
+
+  Set to `null` to disable tagline.
+
+### actions
+
+- Type:
+
+```ts
+Array<{
+  text: string
+  link: string
+  type?: 'primary' | 'secondary'
+}>
+```
+
+- Details:
+
+  Configuration of the action buttons.
+
+- Example:
+
+```md
+---
+actions:
+  - text: Get Started
+    link: /guide/getting-started.html
+    type: primary
+  - text: Introduction
+    link: /guide/
+    type: secondary
+---
+```
+
+### features
+
+- Type:
+
+```ts
+Array<{
+  title: string
+  details: string
+}>
+```
+
+- Details:
+
+  Configuration of the features list.
+
+- Example:
+
+```md
+---
+features:
+  - title: Simplicity First
+    details: Minimal setup with markdown-centered project structure helps you focus on writing.
+  - title: Vue-Powered
+    details: Enjoy the dev experience of Vue, use Vue components in markdown, and develop custom themes with Vue.
+  - title: Performant
+    details: VuePress generates pre-rendered static HTML for each page, and runs as an SPA once a page is loaded.
+---
+```
+
+### footer
+
+- Type: `string`
+
+- Details:
+
+  Specify the content of the footer.
+
+### footerHtml
+
+- Type: `boolean`
+
+- Details:
+
+  Allow HTML in footer or not.
+
+  If you set it to `true`, the [footer](#footer) will be treated as HTML code.
+
+## Normal Page
+
+Frontmatter in this section will only take effect in normal pages.
+
+### editLink
+
+- Type: `boolean`
+
+- Details:
+
+  Enable the _edit this page_ link in this page or not.
+
+- Also see:
+  - [Default Theme > Config > editLink](./config.md#editlink)
+
+### lastUpdated
+
+- Type: `boolean`
+
+- Details:
+
+  Enable the _last updated timestamp_ in this page or not.
+
+- Also see:
+  - [Default Theme > Config > lastUpdated](./config.md#lastupdated)
+
+### contributors
+
+- Type: `boolean`
+
+- Details:
+
+  Enable the _contributors list_ in this page or not.
+
+- Also see:
+  - [Default Theme > Config > contributors](./config.md#contributors)
+### sidebar
+
+- Type: `false | 'auto' | SidebarConfigArray | SidebarConfigObject`
+
+- Details:
+
+  Configure the sidebar of this page.
+
+- Also see:
+  - [Default Theme > Config > sidebar](./config.md#sidebar)
+
+### prev
+
+- Type: `NavLink | string`
+
+- Details:
+
+  Specify the link of the previous page.
+
+  If you don't set this frontmatter, the link will be inferred from the sidebar config.
+
+  To configure the prev link manually, you can set this frontmatter to a `NavLink` object or a string:
+
+  - A `NavLink` object should have a `text` field and a `link` field.
+  - A string should be the path to the target page file. It will be converted to a `NavLink` object, whose `text` is the page title, and `link` is the page route path.
+
+- Example:
+
+```md
+---
+# NavLink
+prev:
+  text: Get Started
+  link: /guide/getting-started.html
+
+# NavLink - external url
+prev:
+  text: GitHub
+  link: https://github.com
+
+# string - page file path
+prev: /guide/getting-started.md
+
+# string - page file relative path
+prev: ../../guide/getting-started.md
+---
+```
+
+### next
+
+- Type: `NavLink | string`
+
+- Details:
+
+  Specify the link of the next page.
+
+  If you don't set this frontmatter, the link will be inferred from the sidebar config.
+
+  The type is the same as [prev](#prev) frontmatter.