Explore dithering for black and white only fast display mode

[Eeems]

https://github.com/rmkit-dev/rmkit/blob/master/src/rmkit/fb/dither.h
https://github.com/rmkit-dev/rmkit/blob/master/src/rmkit/color.h

DITHER(x, y, actual_color)

[Eeems]

for (int i = 0; i < height; i++) {
  for (int j = 0; j < width; j++) { 
    image[i][j] = DITHER(i,j,image[i][j]);
  }
}

[Eeems]

https://github.com/rmkit-dev/rmkit/blob/7edc291646c4a72b7b8a512205646a9ad6586fd6/src/rmkit/color.h#L55-L61

[Eeems]

https://forums.tigsource.com/index.php?topic=40832.msg1363742#msg1363742

[Eeems]

QImage::convertToFormat supports dithering when converting to QImage::Format_Mono. Upon testing it, the rM1 just can't keep up with running the emulator and converting the screen. The rM2 may be able to keep up with its two cores, but it's not really a great option. This already runs the rM1 at an almost constant 100% CPU utilization as-is. So something with extremely low overhead is needed.