Consider loading fonts as static files instead of embedding

[apple502j]

Currently, fonts are embedded in the JavaScript file, and accounts for around 5% of scratch-gui bundle. Serving them as static files could reduce bundle size and allow fonts to be cached for more than a week (or whatever Scratch's deployment cycle is)

This requires asynchronous loading of fonts, but scratch-gui sort of does that already. Legacy Edge does not support FontFace.load but that is already the case with font-loader-hoc, so there should be no difference.