feat: preliminary support for RGB led customisable switches

[3djc]

Adds (untested) support for RGB leds for customisable switches support

@raphaelcoeffic will need that ;D

Should not break existing radio

WARNING there is a little trick on BW radio:

• on radio UI, you can only set only predefined colors (but yaml saves uint32 color value)
• it is expected that Companion will allow you to use a RGB picker to select colors outside of the predefined colors, the radio will in this case display "custom" instead of a color name