Vue-cli3项目中不支持element-ui中的render-content写法

基础平台升级后babel.config.js修改为
```module.exports = {
     presets: [
       "@babel/preset-env"
     ]
   }
```

会导致项目运行不了，因为很多项目中用到了element-ui中的render-content方法

```
renderContent(h, { node, data, store }) {
  return (
    <span class="custom-tree-node">
      <span>{node.label}</span>
      <span>
        <el-button size="mini" type="text" on-click={ () => this.append(data) }>Append</el-button>
        <el-button size="mini" type="text" on-click={ () => this.remove(node, data) }>Delete</el-button>
      </span>
    </span>);
}
```
这种需要安装babel插件
```babel-helper-vue-jsx-merge-props": "^2.0.3",
   "babel-plugin-syntax-jsx": "^6.18.0",
   "babel-plugin-transform-vue-jsx": "^3.7.0",
```
babel.config.js修改为
```module.exports = {
     presets: [
       "@babel/preset-env"
     ],
     plugins:['transform-vue-jsx']
   }
```
然而最简单的方法就是讲babel.config.js修改为
```
module.exports = {
  presets: [
    '@vue/app'
  ]
}
```