option to make individual keys used in a chord mapping usable.

[yshui]

right now if two buttons are used in a chord mapping, they both become unusable. (e.g. if A + B is mapped to Start, individual presses of either A or B are no longer registered). this effectively means we lose one button.

if i want to create a button i need but does not physically exist on the gamepad, chord mapping get very close to that goal but just come a bit short.

[yshui]

would be nice if there is a fallthrough here if translate_chord returned None:

InputPlumber/src/input/event/evdev/translator.rs

Lines 200 to 203 in 8d9c2ac

	return self
	.translate_chord(event)
	.map(|e| vec![e])
	.unwrap_or_default();