Can't remap L2/R2 to not trigger mouse mode

[shaunkane]

Currently, L2 is hard coded to toggle mouse mode and can't be remapped to controller input. Mapping L1/L2 to controller inputs would enable one-handed play and improve customization in general.

Ideally mouse mode would be remappable to another key, but even just disabling the mouse mode function (if the user maps another input to L2 or R2) would be helpful.

[Leemann07]

1. Can't I turn the L2 button function on and off? ( disabling the mouse mode function )
2. When playing pico-8 games with Miyu Mini, I often pressed the L2 button without realizing it.

[XK9274]

Hi, this was committed in:

XK9274/sdl2_miyoo@2caea47

And will go live in Onion when this merges:

OnionUI/Onion#1535

If you want to test it, you can merge those files in the PR - let me know if it works for you, otherwise i'll make changes.