optionOrAlt key for Mac and Windows unification.

[ryanpeach]

Context

There is a modifier commandOrControl for key presses that switches depending on whether or not you are on mac between command (Mac) or control (Windows). Similarly there should be an optionOrAlt key. This is even more intuitive since mac doesn't have an alt, but it does have a seperate control and command key.

I should be able to do this, just noting it down here.

[tmacwill]

thanks for the suggestion! I believe this should be happening already based on:

• https://github.com/serenadeai/driver/blob/master/src/windows.cpp#L283
• https://github.com/serenadeai/driver/blob/master/src/mac.cpp#L699

but, if that's not working please reopen this! commandOrControl exists because Macs have both a command and control key, whereas the option key replaces the alt key.