content: import React from 'react';
  import ReactDOM from 'react-dom';
  import CssBaseline from '@material-ui/core/CssBaseline';
  import { ThemeProvider } from '@material-ui/styles';
  import App from './App';
  import theme from './theme';
  
  function Main() {
    React.useEffect(() => {
      const jssStyles = document.querySelector('#jss-server-side');
      if (jssStyles) {
        jssStyles.parentNode.removeChild(jssStyles);
      }
    }, []);
  
    return (
      <ThemeProvider theme={theme}>
        {/* CssBaseline kickstart an elegant, consistent, and simple baseline to build upon. */}
        <CssBaseline />
        <App />
      </ThemeProvider>
    );
  }
  
  ReactDOM.hydrate(<Main />, document.querySelector('#root'));
  