Gamecube Controller Adapter Support

[rumia1]

I would like to see support for the official Gamecube controller adapter if possible. I can use most Nintendo controllers through Steam including Switch JoyCons, Wii remotes, and even NES, SNES and N64 controllers via the NSO controllers, but still can't use the GCC adapter for the Wii U/Switch unless I use a 3rd party adapter.