Add support for 12 bit color (RGB444)

[cosmikwolf]

This issue is dependent on RGB444 and BRG444 being added to embedded-graphics pixelcolor, but I figured it would be good to create this bug to track the issue as well.

Adding 12 bit color support would result in a 25% decrease in the time it takes to write color data to a display compared to 16 bit colors, utilizing the RGB444 mode as exists on chips like the ST7789