Provide SDL2 button mappings for convenience

[emilyst]

I'm opening this issue to split off SDL2 mapping discussion from issue #7. Please refer to that issue for context.

Quoting from https://github.com/emilyst/hid-nx-dkms/issues/7#issuecomment-1523843003:

Looking for SDL mappings for https://github.com/gabomdq/SDL_GameControllerDB, both wired and wireless. Mapping tool: https://www.generalarcade.com/gamepadtool/ I have the SNES and N64 pads and got those covered, but not the Genesis.

Okay, I think I see. You want someone to run that program and supply you the output.

I think your request should go into a new issue. If you want to open a dedicated issue, please do. If you have a new topic to discuss, even if it's related to an existing one, it's encouraged to open a new issue for that topic. That way it's easier for myself and others to keep track of.

This has gotten pretty off-topic for six-button Genesis controller support, so I'd like to ask that we stop discussing the SDL mappings here.

I think I can find time today to try to run that program with a three-button controller using the hid-nx module, but I am not certain. This request is a little beyond the scope of a problem, bug, or other issue with my module, so it's a lower priority.