翻訳前のarray-refs.mdファイルを追加

以下ファイルを追加
https://github.com/vuejs/docs-next/blob/master/src/guide/migration/array-refs.md

Author: daisuke85a

src/.vuepress/config.js

@@ -111,6 +111,7 @@ const sidebar = {
       collapsable: true,
       children: [
         'migration/introduction',
+        'migration/array-refs',
         'migration/async-components',
         'migration/attribute-coercion',
         'migration/custom-directives',

src/guide/migration/array-refs.md

@@ -0,0 +1,69 @@
+---
+title: v-for Array Refs
+badges:
+- breaking
+---
+
+# {{ $frontmatter.title }} <MigrationBadges :badges="$frontmatter.badges" />
+
+In Vue 2, using the `ref` attribute inside `v-for` will populate the corresponding `$refs` property with an array of refs. This behavior becomes ambiguous and inefficient when there are nested `v-for`s present.
+
+In Vue 3, such usage will no longer automatically create an array in `$refs`. To retrieve multiple refs from a single binding, bind `ref` to a function which provides more flexibility (this is a new feature):
+
+```html
+<div v-for="item in list" :ref="setItemRef"></div>
+```
+
+With Options API:
+
+```js
+export default {
+  data() {
+    return {
+      itemRefs: []
+    }
+  },
+  methods: {
+    setItemRef(el) {
+      this.itemRefs.push(el)
+    }
+  },
+  beforeUpdate() {
+    this.itemRefs = []
+  },
+  updated() {
+    console.log(this.itemRefs)
+  }
+}
+```
+
+With Composition API:
+
+```js
+import { ref, onBeforeUpdate, onUpdated } from 'vue'
+
+export default {
+  setup() {
+    let itemRefs = []
+    const setItemRef = el => {
+      itemRefs.push(el)
+    }
+    onBeforeUpdate(() => {
+      itemRefs = []
+    })
+    onUpdated(() => {
+      console.log(itemRefs)
+    })
+    return {
+      itemRefs,
+      setItemRef
+    }
+  }
+}
+```
+
+Note that:
+
+- `itemRefs` doesn't have to be an array: it can also be an object where the refs are set by their iteration keys.
+
+- This also allows `itemRefs` to be made reactive and watched, if needed.