content: import React from 'react';
  import { render } from 'react-dom';
  import { renderToStaticMarkup, renderToString } from 'react-dom/server';
  
  import Layout from './components/Layout';
  import Index from './components/IndexPage';
  
  if (typeof document !== 'undefined') {
      render(<Index />, document.getElementById('app'));
  }
  
  export default (locals, cb) => {
      const app = renderToString(<Index />);
      const html = renderToStaticMarkup(<Layout app={app} />);
      cb(null, '<!DOCTYPE html>' + html);
  };
  