Use fast-async for async/await support

Created by: timdorr

fast-async is based on nodent, a generator-optional implementation of async/await support.

By default, it does not use generators, which saves the usage of regenerator if generator functions are not otherwise used. It is also significantly faster, with order-of-magnitude perf gains on mobile browsers in particular.

It also smaller, reducing gzipped file size by 1.44KB in a simple test case:

File sizes after gzip:

  48.7 KB (+1.44 KB)  build/static/js/main.c60c74db.js
  289 B               build/static/css/main.9a0fe4f1.css

Test case code:

class App extends Component {
  async componentDidMount() {
    try {
      const response = await fetch('https://jsonplaceholder.typicode.com/posts/1');
      const data = await response.json();
      console.log(data);
    } catch (lol) {
      alert('oh noes')
    }
  }

  //...
}

I'm not an expert on this library, so there may be further gains to be had from better tuning. But on the surface, we're already getting a good bump on both speed and size.