docs: Add type definition for globalProperties in TypeScript chapter

vuejs/docs@8c9ebf1#diff-c8904f42c96ea728eea302e9bc39484fbb58d2401b4017ad37ea848fc8f183e5

Author: naokie

src/guide/typescript-support.md

@@ -153,6 +153,52 @@ const Component = defineComponent({
 })
 ```
 
+### Augmenting Types for `globalProperties`
+
+Vue 3 provides a [`globalProperties` object](../api/application-config.html#globalproperties) that can be used to add a global property that can be accessed in any component instance. For example, a [plugin](./plugins.html#writing-a-plugin) might want to inject a shared global object or function.
+
+```ts
+// User Definition
+import axios from 'axios'
+
+const app = Vue.createApp({})
+app.config.globalProperties.$http = axios
+
+// Plugin for validating some data
+export default {
+  install(app, options) {
+    app.config.globalProperties.$validate = (data: object, rule: object) => {
+      // check whether the object meets certain rules
+    }
+  }
+}
+```
+
+In order to tell TypeScript about these new properties, we can use [module augmentation](https://www.typescriptlang.org/docs/handbook/declaration-merging.html#module-augmentation).
+
+In the above example, we could add the following type declaration:
+
+```ts
+import axios from 'axios'
+
+declare module '@vue/runtime-core' {
+  export interface ComponentCustomProperties {
+    $http: typeof axios
+    $validate: (data: object, rule: object) => boolean
+  }
+}
+```
+
+We can put this type declaration in the same file, or in a project-wide `*.d.ts` file (for example, in the `src/typings` folder that is automatically loaded by TypeScript). For library/plugin authors, this file should be specified in the `types` property in `package.json`.
+
+::: warning Make sure the declaration file is a TypeScript module
+In order to take advantage of module augmentation, you will need to ensure there is at least one top-level `import` or `export` in your file, even if it is just `export {}`.
+
+[In TypeScript](https://www.typescriptlang.org/docs/handbook/modules.html), any file containing a top-level `import` or `export` is considered a 'module'. If type declaration is made outside of a module, it will overwrite the original types rather than augmenting them.
+:::
+
+For more information about the `ComponentCustomProperties` type, see its [definition in `@vue/runtime-core`](https://github.com/vuejs/vue-next/blob/2587f36fe311359e2e34f40e8e47d2eebfab7f42/packages/runtime-core/src/componentOptions.ts#L64-L80) and [the TypeScript unit tests](https://github.com/vuejs/vue-next/blob/master/test-dts/componentTypeExtensions.test-d.tsx) to learn more.
+
 ### 戻り値の型にアノテーションをつける
 
 Vue の型宣言ファイルの循環的な性質により、TypeScript は算出プロパティの型を推論することが困難な場合があります。この理由により、算出プロパティの戻り値の型にアノテーションをつける必要があります。
@@ -170,7 +216,7 @@ const Component = defineComponent({
     // アノテーションが必要です
     greeting(): string {
       return this.message + '!'
-    }
+    },
 
     // セッターを持つ算出プロパティのでは、ゲッターにアノテーションが必要です
     greetingUppercased: {
@@ -179,8 +225,8 @@ const Component = defineComponent({
       },
       set(newValue: string) {
         this.message = newValue.toUpperCase();
-      },
-    },
+      }
+    }
   }
 })
 ```