[Keyboard] Add KBD67 MKII Solderable PCB Variant (#7202)

[Keyboard] Add KBD67 MKII Solderable PCB Variant (#7202)

* Clone 8x source to begin

* Start replacing stuff

* Get things compiling

* Rename files

* Move board files to match MKII RGB files

* Adjust readme

* Adjust main keymap to be functional

* Make defualt keymap more basic; add personal keymap

* Remove unnecessary trailing slashes from keymap

* Remove unused functions from keymaps

* Remove obsolete build flags

* Adjust comments as requested

* Apply suggestions from code review

Co-Authored-By: noroadsleft <18669334+noroadsleft@users.noreply.github.com>
* Adjust as suggested

* Fix broken compile following applying suggestions