https://reactjs.org/docs/code-splitting.html#reactlazy

2018
https://medium.com/@pomber/lazy-loading-and-preloading-components-in-react-16-6-804de091c82d
https://dev.to/vigzmv/reactlazy-what-and-how-to-use-in-your-app-p9a
    http://vigneshm.com/react-lazy-example/
    https://github.com/vigzmv/react-lazy-example