一、Vue3 中 Teleport 的作用是什么？
    将一个元素挂载到一个指定的dom元素上；示例：

    1. <body>
    2.   <div id="app" style="position: relative;">
    3.     <h3>Tooltips with Vue 3 Teleport</h3>
    4.     <div>
    5.       <modal-button></modal-button>
    6.     </div>
    7.   </div>
    8. const app = Vue.createApp({});
    10. app.component('modal-button', {
    11.   template: `
    12.     <button @click="modalOpen = true">
    13.         Open full screen modal! (With teleport!)
    14.     </button>
    16.     <teleport to="body">
    17.       <div v-if="modalOpen" class="modal">
    18.         <div>
    19.           I'm a teleported modal! 
    20.           (My parent is "body")
    21.           <button @click="modalOpen = false">
    22.             Close
    23.           </button>
    24.         </div>
    25.       </div>
    26.     </teleport>
    27.   `,
    28.   data() {
    29.     return { 
    30.       modalOpen: false
    31.     }
    32.   }
    33. })
    35. app.mount('#app')
    36. </body>

    二、说一下vue3的composition api?
    函数式编程，提供了一些列新的api