[FEAT] Transparent keycodes

[meir]

Is your feature request related to a problem? Please describe.
Transparent keycodes should be added so that layers dont have to require each keycode to be set for the same functions
Transparent keys would get the first non-transparent key from the layer below

Describe the solution you'd like
Add a transparent keycode that will act like the first non-transparent keycode in the layer indices below

Describe alternatives you've considered
N/A

Additional context
N/A