The README mentions a `setupProxy.js` file and links to [the advanced proxy setup guide of CRA](https://facebook.github.io/create-react-app/docs/proxying-api-requests-in-development#configuring-the-proxy-manually) (link could be updated, it links to an out-dated one). But there is no `src/setupProxy.js` file. Am I missing something or is this file just missing?