Support for different color modes

[dwijtsma]

Hello,

Is it possible to have support for different color modes like 12 and 18 bit?

I found b"\x3a\x01\x05" # COLMOD - 16bit color in the init sequence.
I expect it is not enough to change this to `b"\x3a\x01\x03" to get 12 bit support. Data send to the display also needs to be in a different format.