This will let us register the app.css in webpack from a context, and potentially
have a configuration such as:
```
const appCssContext = require.context("~/", false, /^\.\/app\.(css|scss|less|sass)$/);
global.registerWebpackModules(appCssContext);
```
That will work with all of the app.css, app.scss, app.less etc. without further manual reconfiguration.