Add note about how dit doesn't support mixed-type alphabets.
Add note about how dit doesn't support mixed-type alphabets.

dit/dit,chebee7i/dit,chebee7i/dit,chebee7i/dit,Autoplectic/dit,chebee7i/dit,dit/dit,dit/dit,dit/dit,Autoplectic/dit,Autoplectic/dit,Autoplectic/dit,Autoplectic/dit,dit/dit