Retroarch-assets - Assets needed for RetroArch - e.g. menu drivers, etc

Description:
The retroarch-assets repository is the home of the user interface elements
used to generate the various User Experience (UX) environments. The UX
environments are referred to as “menu drivers” and you can switch between
environments on most platforms at any time.

Rationale:
This more like re-review. RetroArch now using release tags for their sub-projects like assets, databases, etc (see: FR: Version tags · Issue #414 · libretro/retroarch-assets · GitHub). Splitting RPM sub-packages to separate packages will make it easier updating/building RetroArch and all its stuff. It also could simplify Spec file for RPM Fusion build and speedup building process, save disc space (assets SRPM itself is about ~470MB).

retroarch-assets would be better to keep as weak dep since some users still prefer to download it manually from app itself.

Review procces should be trivial for this package.

https://bugzilla.redhat.com/show_bug.cgi?id=2337051