Add new 4x12 ortho layout & add credit to XD75 port (#1782)

Add new 4x12 ortho layout & add credit to XD75 port (#1782)

* add xd75, preliminary RGB'

* fix RGB

* add backlight support (probably)

* updated readme and tweaked keymap

* added xd75 to list in /keyboards

* copyright ALL the things, create blank slate for Colemak Mod-DH Split/Wide keymap

* Add preliminary split Colemak Mod-DH layout

* changing stuff to compile properly

* attribution

* moar attribution

* removed incomplete keymap

* Create Colemak Mod-DH Wide layout for 4x12 ortho.

* Move Adjust key

* Add layou timage to readme

* fix naming

* Fix stupid issue with not understanding how the keymap works

* forgot to switch COLEMAK to COLEMAKDH...

* Remove and link image

* Remove and link image