Moves the 256 entry GAMMA table into pimoroni_common.
Should probably be added into a library so MicroPython is built with only one instance of the table.
"RGBLED" PWMs 3 pins as a single RGB LED and exposes methods to set the colour via HSV/RGB.
"Button" handles tracking the state and changed state of a single GPIO button, in addition to supporting auto-repeat for held-down buttons.