Maps key and gamepad events to actions in Bevy. See the example for usage.

I'll be the first to admit that this crate needs some polish. Things it seems to do right:

• Binds string actions to single or multiple keycodes, gamepad buttons, or stick motions. Not sure that cross-input gestures work (I.e. gamepad buttons and keys).
• Binds the same action to multiple distinct input types. The same action can be bound to a key, gamepad button, etc.
• Resolves key/button conflicts. Binding actions to Enter, Ctrl-Enter and Ctrl-Alt-Enter only runs a single action if Ctrl-Alt-Enter is pressed.

Things that don't work and that I'd appreciate help with:

• Mouse gestures. PRs welcome.
• Serialization of keybindings. PRs welcome.
• Probably a million other things. PRs welcome.