Add a way to detect key release in livesplit-hotkey

[Roger]

Currently is only possible to detect keys pressed, but not the release event.

Had a look at the linux implementations and should be simple (didn't check mac/win/wasm), but I don't think that there's a way to make this backwards compatible other than creating another register/unregister methods.

Would you consider something like this? what would be a good api? new methods? an argument in the callback with some enum with KeyDown/KeyUp? another optional callback for the release?

[CryZe]

Mmh, I'm not sure this makes sense for our use case, cause it's not a generic keyboard API and instead specifically a hotkey listener where you want to know when the hotkey is pressed, especially in our case where the timing is really important.