Modrinth Platform Support For Pff

[Andy-K-Sparklight]

As Alicorn found out that many mods cannot be found on CurseForge, but on Modrinth instead, we've noticed that the requirement of Modrinth mods install is increasing.

Though, add support for Modrinth isn't easy, probably we need to rewrite the virtual layer and add a new adaptor.

If anypony can offer us some help, we will be very grateful!