This changes how key caching & lookup works: instead of updating the whole key
cache whenever we change the layer state, we update each key before they are
pressed or released. This allows us to have two different ways in which layers
can work:
- Keys still held when releasing the layer key will be masked out until they are
released. (This is the current behaviour)
- Keys held will repeat the keycode they had when they toggled on, even if the
layer key gets released prior to this other key, while other keys will not be
affected.
One can toggle between the two modes by setting
`Kaleidoscope.repeat_first_press` to `true` (second behaviour) or `false` (first
behaviour).
For now, the default behaviour is left unchanged.
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>