Style lock, latch, and press separately
Inspired by #89 (closed).
There should be a separate CSS rule for buttons in a locked state, like:
:stuck { color: foo }
Shift_L:stuck { color: foo }
Shift_L:locked { color: foo }
Stuck in this context is "will get unstuck on next press", and "locked" is "will stay until pressed".
@tobias.bernard please label as "wishlist" if we don't need it now, and remove "needsdesign" when you've had a look.
Edited by Dorota Czaplejewicz