解决：peer vue@"^2.5.17" from element-ui@2.15.8

element-ui不适配vue3，官方已将vue3版本的更新为element-plus

解决：
npm install element-plus --save

引入

import { createApp } from 'vue'
import ElementPlus from 'element-plus'
import 'element-plus/dist/index.css'
import App from './App.vue'

const app = createApp(App)

app.use(ElementPlus)
app.mount('#app')

https://element-plus.org/zh-CN/guide/installation.html#%E7%89%88%E6%9C%AC