Fix style support
Fix style support

SASS will be compiled if `src/ui/styles/app.scss` is present.

Otherwise, all CSS in `src/ui/styles` will be concat’d.

This is preliminary, but should be safe, and is compatible with
Module Unification. We’re not taking a stance on colocation (yet).
glimmerjs/glimmer-application-pipeline,glimmerjs/glimmer-application-pipeline,glimmerjs/glimmer-application-pipeline