警告内容:
Warning: findDOMNode is deprecated in StrictMode. findDOMNode was passed an instance of Wave which is inside StrictMode. Instead, add a ref directly to the element you want to reference. Learn more about using refs safely here: https://fb.me/react-strict-mode-find-node
我只要用antd的组件就会有警告存在
警告原因：
是因为 react 中的严格模式: StrictMode
解决办法:
在index.js中挂载 App 的外面有这样一个标签
只要把这个标签删除掉就可以了