Determine how to use Rails 7 CSS processing

[jazairi]

This app currently uses sassc, which is unsupported. The processors recommended for use in Rails 7 (dartsass, cssbundler, etc.) require an installation step that is unclear how to execute in a Rails engine.

[jazairi]

Background on the changes to CSS processing in Rails 7: https://jasonfleetwoodboldt.com/2022/01/24/the-day-that-rails-ejected-node/
Migrating to cssbundling-rails: https://dev.to/kolide/how-to-migrate-a-rails-6-app-from-sass-rails-to-cssbundling-rails-4l41