Cartoon + monochrome shader (2nd attempt)

Addition of cartoon and monochrome shaders. Hopefully this time it
merges properly.
Minor change to "Timothy Lottes' CRT"

Per Boulotaur2024's request, changed;

float2 res = SCREEN_SIZE / 3.0
to
float2 res = SCREEN_SIZE / 6.0
Merge pull request #216 from One3rd/master

Cartoon + monochrome shader (2nd attempt)