message: docs(Popup): use composition api
diff: @@ -20,18 +20,19 @@ app.use(Popup);
  ```
  ```js
  +import { ref } from 'vue';
  +
  export default {
  - data() {
  + setup() {
  + const show = ref(false);
  + const showPopup = () => {
  + show.value = true;
  + };
  return {
  - show: false,
  + show,
  + showPopup,
  };
  },
  -
  - methods: {
  - showPopup() {
  - this.show = true;
  - },
  - },
  };
  ```
  @@ -86,20 +87,23 @@ Use `position` prop to set popup display position.
  Use `teleport` prop to specify mount location.
  ```html
  -<!-- mount to body -->
  +<!-- teleport to body -->
  <van-popup v-model:show="show" teleport="body" />
  -<!-- mount to #app -->
  +<!-- teleport to #app -->
  <van-popup v-model:show="show" teleport="#app" />
  -<!-- mount to Element -->
  +<!-- teleport to Element -->
  <van-popup v-model:show="show" :teleport="myContainer" />
  ```
  ```js
  export default {
  - beforeCreate() {
  - this.myContainer = document.querySelector('.my-container');
  + setup() {
  + const myContainer = document.querySelector('.my-container');
  + return {
  + myContainer,
  + };
  },
  };
  ```
  