Deal with the app being served through NPM vs development

[radekstepan]

Served through NPM should use the minified JS and CSS resources, while development the ones with a source map while preserving being able to serve through GitHub Pages. Essentially we need to serve a different index.html file in each case. So:

1. For GitHub Pages and NPM app we use a static index.html file that points to a minified version of the app.
2. For development we use a flag that injects a dynamic index.html file pointing to unminified builds.