chore: changelog for 1.9.2

Author: ulivz

Diff for: changelog/1.9.2.md

@@ -0,0 +1,116 @@
+# TS Support for VuePress Plugin and Theme.
+
+## Motivation
+
+We've announced [VuePress 1.9](https://github.com/vuejs/vuepress/releases/tag/v1.9.0) that takes full TypeScript Support for Config File, while VuePress 1.9.2 ships with **TS Support for VuePress Plugin and Theme**:
+
+<p align="center">
+    <img src="./assets/showcase.png" width="400px"></img>
+<p>
+
+## Quick Start
+
+In order to make the plugin developer not dependent on VuePress for development, we provide a completely independent type package `@vuepress/types`:
+
+```bash
+npm i @vuepress/types -D
+```
+
+`@vuepress/types` exports four functions:
+
+- `defineConfig`
+- `defineConfig4CustomTheme`
+- `defineTheme`
+- `definePlugin`
+
+Note that using `@vuepress/types` is equivalent to using `vuepress/config`.
+
+## Plugin Type
+
+If you already have some VuePress plugins written in JS, you can leverage your IDE's intellisense with jsdoc type hints:
+
+```js
+/**
+ * @type {import('@vuepress/types').Plugin}
+ */
+module.exports = {
+  ready() {
+    // ...
+  }
+};
+```
+
+Alternatively, you can use the defineConfig helper which should provide intellisense without the need for jsdoc annotations:
+
+```js
+import { definePlugin } from "@vuepress/types";
+
+export default definePlugin({
+  // ...
+});
+```
+
+## Plugin Options Type
+
+Type of plugin options also supports passing in through generic type:
+
+```ts
+import { definePlugin } from "@vuepress/types";
+
+interface Options {
+  name: string;
+}
+
+export default definePlugin<Options>((options, ctx) => {
+  return {
+    ready() {
+      return ctx.base + options.name;
+    }
+  };
+});
+```
+
+## Theme Type
+
+Similar to [plugin](plugin-type), the only difference is the type you use, and the define function:
+
+```diff
+ /**
+- * @type {import('@vuepress/types').Plugin}
++ * @type {import('@vuepress/types').Theme}
+  */
+```
+
+```diff
+-import { definePlugin } from "@vuepress/types";
++import { defineTheme } from "@vuepress/types";
+
+-export default definePlugin({
++export default defineTheme({
+   // ...
+ });
+```
+
+## Theme Config Type
+
+Type of theme config also supports passing in through generic type:
+
+```ts
+import { defineTheme } from "@vuepress/types";
+
+interface ThemeConfig {
+  lang: string;
+}
+
+export default defineTheme<ThemeConfig>((themeConfig, ctx) => {
+  return {
+    ready() {
+      return ctx.base + themeConfig.lang;
+    }
+  };
+});
+```
+
+## Notes
+
+It is worth noting that, unlike the [site configuration](https://vuepress.vuejs.org/config/), i.e. `.vuepress/config.js`, if you use TypeScript to write theme or plugin, you still need to compile it into JavaScript before publishing it to NPM.