Prepare our packaging process to work with standard CSS embedding

[oliversturm]

I'm using this as an example for something that's less than optimal in our packager. There might be other similar issues.

I was updating a project based on one of the templates to a current version of react-bootstrap. I read the official instructions and found that I'm supposed to do this:

import 'bootstrap/dist/css/bootstrap.min.css';

In the template however, a CSS file is instead injected using Helmet. I found that the import approach fails with a very long and cryptic error message - I don't know if this is just because there are webpack modules missing for the purpose, or because our packager can't deal with this... but I think we should prepare things so that users can follow standard installation instructions without having to modify basic project configuration aspects like webpack. CSS embedding is certainly a very standard thing and should work out of the box.

(Note - react-bootstrap worked correctly when I copied the CSS file to the static folder and used Helmet as before.)