VIA support for the KBDFans KBD6x (#8680)

* Add VIA keymap

* Update VID/PID

- Update VID/PID to match other KBDfans keyboards
- Flesh out keyboard description

* add missing newline. whoops.

* Update keyboards/kbdfans/kbd6x/keymaps/via/rules.mk

Co-Authored-By: Drashna Jaelre <drashna@live.com>

* update author / copyright date

* Update keyboards/kbdfans/kbd6x/keymaps/via/rules.mk

Co-Authored-By: Ryan <fauxpark@gmail.com>

* Update keyboards/kbdfans/kbd6x/keymaps/via/keymap.c

Co-Authored-By: Joel Challis <git@zvecr.com>

* Update keyboards/kbdfans/kbd6x/kbd6x.h

Co-Authored-By: Joel Challis <git@zvecr.com>

Co-authored-by: George Wietor <george@light-gray.attlocal.net>
Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: Joel Challis <git@zvecr.com>

keyboards/kbdfans/kbd6x/keymaps/via/readme.md

@@ -0,0 +1,7 @@
+# VIA keymap for KBDFans KBD6x.
+
+Predefined Layers:
+- 0 - Default KBD6x keymap
+- 1 - A modified version of the classic HHKB function layer
+- 2 - Lighting control and RESET
+- 3 - Blank