message: docs(DropdownMenu): use composition api
diff: @@ -17,27 +17,35 @@ app.use(DropdownItem);
  ```html
  <van-dropdown-menu>
  - <van-dropdown-item v-model="value1" :options="option1" />
  - <van-dropdown-item v-model="value2" :options="option2" />
  + <van-dropdown-item v-model="state.value1" :options="option1" />
  + <van-dropdown-item v-model="state.value2" :options="option2" />
  </van-dropdown-menu>
  ```
  ```js
  +import { reactive } from 'vue';
  +
  export default {
  - data() {
  - return {
  + setup() {
  + const state = reactive({
  value1: 0,
  value2: 'a',
  - option1: [
  + });
  + const option1 = [
  { text: 'Option1', value: 0 },
  { text: 'Option2', value: 1 },
  { text: 'Option3', value: 2 },
  - ],
  - option2: [
  + ];
  + const option2 = [
  { text: 'Option A', value: 'a' },
  { text: 'Option B', value: 'b' },
  { text: 'Option C', value: 'c' },
  - ],
  + ];
  +
  + return {
  + state,
  + option1,
  + option2,
  };
  },
  };
  @@ -47,16 +55,16 @@ export default {
  ```html
  <van-dropdown-menu>
  - <van-dropdown-item v-model="value" :options="option" />
  + <van-dropdown-item v-model="state.value" :options="option" />
  <van-dropdown-item title="Title" ref="item">
  <van-cell center title="Title">
  <template #right-icon>
  - <van-switch v-model="switch1" size="24" active-color="#ee0a24" />
  + <van-switch v-model="state.switch1" size="24" active-color="#ee0a24" />
  </template>
  </van-cell>
  <van-cell center title="Title">
  <template #right-icon>
  - <van-switch v-model="switch2" size="24" active-color="#ee0a24" />
  + <van-switch v-model="state.switch2" size="24" active-color="#ee0a24" />
  </template>
  </van-cell>
  <div style="padding: 5px 16px;">
  @@ -69,23 +77,31 @@ export default {
  ```
  ```js
  +import { ref, reactive } from 'vue';
  +
  export default {
  - data() {
  - return {
  + setup() {
  + const item = ref(null);
  + const state = reactive({
  value: 0,
  switch1: false,
  switch2: false,
  - option: [
  + });
  + const options = [
  { text: 'Option1', value: 0 },
  { text: 'Option2', value: 1 },
  { text: 'Option3', value: 2 },
  - ],
  + ];
  + const onConfirm = () => {
  + item.value.toggle();
  + };
  +
  + return {
  + item,
  + state,
  + option,
  + onConfirm,
  };
  - },
  - methods: {
  - onConfirm() {
  - this.$refs.item.toggle();
  - },
  },
  };
  ```
  