halftone support

[TiceRex]

I can see there are some halftone fonts available, but I think halftone support could be extended to any font by using a simple algorithm.
Just before sending the pattern to the display, you should apply AND with 0x55 or 0xAA alternately:

if (halftone == 1) { p = p & (((d%2)+1)*0x55); };

where p is the pattern to be displayed, and d is the horizontal position of the pattern.

Small fonts (i.e. 8 bit height) fall apart using this method, but the bigger ones (16 or more bits height) display nicely.

[olikraus]

It should be simple to do this, by using the Direct Access API: https://github.com/olikraus/u8g2/wiki/u8g2reference#direct-access-buffer-api