Resolve css standard discrepancy between mapbox-gl-rails 2.9.0 and sassc-ruby

[rudokemper]

The latest 2.9.0 version of Mapbox GL Rails allows us to implement some of Mapbox's latest features, including the new globe projection. However recent changes in this codebase to the CSS formatting - specifically, a rgb(x x x / x%) standard - causes the gem to break with SCSS because of this issue which happens because SASS is not yet supporting this standard.

Since sassc-ruby is not being maintained at the moment, we need to figure out how to resolve this issue before bumping the Mapbox GL Rails gem to 2.9.0.

With the refactor, we are moving away from Administrate, but are we otherwise reliant on SASS that will cause issues? Or do we need to move to another library like sass-embedded or use one of the stop gap solutions described here?

👀 @lauramosher