[Keyboard] Add support for XD004 macro keyboard (#6337)

* Add support for XD004

Also applying the following suggested edits:

Add hardware availability link in readme
Co-Authored-By: Drashna Jaelre <drashna@live.com>
Enable lite bootmagic
Co-Authored-By: Drashna Jaelre <drashna@live.com>
Remove commented out MCU
Co-Authored-By: fauxpark <fauxpark@gmail.com>
* Add more ellaborate keymap

Correcting usage of tap_code_16 for modified key, thanks to @drashna

* Add information about bootloader type

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