docs: add extendsPageOptions hook

Author: meteorlxy

docs/.vuepress/public/images/guide/vuepress-core-process.png

@@ -22,7 +22,8 @@ The above figure shows the core process of VuePress Node App and the hooks of [P
 
 - In the **init** stage:
   - Theme and plugins will be loaded. That means all the plugins should be used before initialization.
-  - Page files will be loaded. As we are using markdown-it to parse the markdown file, the [extendsMarkdown](../../reference/plugin-api.md#extendsmarkdown) hook will be processed before that.
+  - As we are using markdown-it to parse the markdown file, the [extendsMarkdown](../../reference/plugin-api.md#extendsmarkdown) hook will be processed before loading page files.
+  - Page files will be loaded, and [extendsPageOptions](../../reference/plugin-api.md#extendspageoptions) hook will be processed to create pages.
 - In the **prepare** stage:
   - Temp files will be generated, so all hooks related to client files will be processed here.
 - In the **dev / build** stage:

docs/guide/advanced/architecture.md

@@ -9,6 +9,7 @@ Plugins should be used before initialization. The basic options will be handled
 The following hooks will be processed when initializing app:
 
 - [extendsMarkdown](#extendsmarkdown)
+- [extendsPageOptions](#extendspageoptions)
 - [onInitialized](#oninitialized)
 
 The following hooks will be processed when preparing files:
@@ -168,6 +169,35 @@ module.exports = {
 }
 ```
 
+### extendsPageOptions
+
+- Type: `(filePath: string, app: App) => PageOptions | Promise<PageOptions>`
+
+- Details:
+
+  Page options extension.
+
+  This hook accepts a function that will receive the relative file path of the page. The returned object will be merged into page options, which will be used to create the page.
+
+- Example:
+
+Set permalink pattern for pages in `_posts` directory:
+
+```js
+module.exports = {
+  extendsPageOptions: (filePath) => {
+    if (filePath.startsWith('_posts/')) {
+      return {
+        frontmatter: {
+          permalinkPattern: '/:year/:month/:day/:slug.html',
+        },
+      }
+    }
+    return {}
+  },
+}
+```
+
 ### extendsPageData
 
 - Type: `(page: Page, app: App) => Record<string, any> | Promise<Record<string, any>>`
@@ -189,7 +219,7 @@ module.exports = {
 }
 ```
 
-  In client component:
+In client component:
 
 ```js
 import { usePageData } from '@vuepress/client'

docs/reference/plugin-api.md

@@ -22,7 +22,8 @@
 
 - 在 **init** 阶段：
   - 主题和插件会被加载。这意味着插件需要在初始化之前使用。
-  - 页面文件会被加载。由于我们要使用 markdown-it 来解析 Markdown 文件，因此 [extendsMarkdown](../../reference/plugin-api.md#extendsmarkdown) 会在这之前调用。
+  - 由于我们要使用 markdown-it 来解析 Markdown 文件，因此 [extendsMarkdown](../../reference/plugin-api.md#extendsmarkdown) 会在加载页面文件之前调用。
+  - 页面文件会被加载，因此 [extendsPageOptions](../../reference/plugin-api.md#extendspageoptions) Hook 会被调用，用以创建页面。
 - 在 **prepare** 阶段：
   - 临时文件会被生成，因此所有和客户端文件相关的 Hooks 会在此处调用。
 - 在 **dev / build** 阶段：

docs/zh/guide/advanced/architecture.md

@@ -9,6 +9,7 @@
 下列 Hooks 会在初始化 App 时处理：
 
 - [extendsMarkdown](#extendsmarkdown)
+- [extendsPageOptions](#extendspageoptions)
 - [onInitialized](#oninitialized)
 
 下列 Hooks 会在准备文件时处理：
@@ -168,6 +169,35 @@ module.exports = {
 }
 ```
 
+### extendsPageOptions
+
+- 类型： `(filePath: string, app: App) => PageOptions | Promise<PageOptions>`
+
+- 详情：
+
+  页面配置项扩展。
+
+  该 Hook 接收一个函数，在参数中会收到页面文件的相对路径。返回的对象会被合并到页面配置项中，用以创建页面。
+
+- 示例：
+
+为 `_posts` 目录下的页面设置永久链接 Pattern ：
+
+```js
+module.exports = {
+  extendsPageOptions: (filePath) => {
+    if (filePath.startsWith('_posts/')) {
+      return {
+        frontmatter: {
+          permalinkPattern: '/:year/:month/:day/:slug.html',
+        },
+      }
+    }
+    return {}
+  },
+}
+```
+
 ### extendsPageData
 
 - 类型： `(page: Page, app: App) => Record<string, any> | Promise<Record<string, any>>`