doc(useMutationObserver): convert the <script> section to <script setup lang="ts"> format

pkc918 · pkc918 · commit cf8369d5dd36 · 2025-07-22T11:06:50.000+08:00
diff --git a/packages/core/useMutationObserver/index.md b/packages/core/useMutationObserver/index.md
@@ -8,26 +8,19 @@ Watch for changes being made to the DOM tree. [MutationObserver MDN](https://dev
 
 ## Usage
 
-```ts
+```vue
+<script setup lang="ts">
 import { useMutationObserver } from '@vueuse/core'
 import { ref, useTemplateRef } from 'vue'
 
-export default {
-  setup() {
-    const el = useTemplateRef('el')
-    const messages = ref([])
+const el = useTemplateRef('el')
+const messages = ref([])
 
-    useMutationObserver(el, (mutations) => {
-      if (mutations[0])
-        messages.value.push(mutations[0].attributeName)
-    }, {
-      attributes: true,
-    })
-
-    return {
-      el,
-      messages,
-    }
-  },
-}
+useMutationObserver(el, (mutations) => {
+  if (mutations[0])
+    messages.value.push(mutations[0].attributeName)
+}, {
+  attributes: true,
+})
+</script>
 ```
