Adds basic support for u/flehrad's bigswitch pcb (#3015)

Adds basic support for u/flehrad's bigswitch pcb (#3015)

* Adds basic support for u/flehrad's bigswitch pcb

 - also adds support for OSX Eject/Power
   The function of this key depends on the version of OSX and if you
   have physical media. For a macbook pro 2017 holding this key down
   brings up the shutdown dialog. If you wrap it in LCTL and LSFT the
   screenlock turns on immediately.

* Switch to Layout Macro

 - add a code for OSX Sleep

* Add a README

* Turn on RGB by default

* Add info.json

* Address comments by @drashna

* Only define Eject in keymap