[Keyboard] 40percent.club's Half 'n' half keyboard port (#5005)

* fixed arrow keys and left control

* added right shift

* latest version

* reverted arrow keys

* edited readme

* added osu layer

* updated osu layout

* updated osu layout

* added full arrow keys to osu layout

* in case i mess up creating macros

* added the best meme key in the world

* added plover steno layer

* updated boy314 layout

* removed unused layers

* added boy314 xd75 layout, inspired by preonic layout

* added boy314 xd75 layout, inspired by preonic layout

* version 2 of boy314's xd75 layout

* added readme notes

* updated readme for boy314 xd75 layout

* qwerty support, brackets on bottom row, caps lock underglow

* fixed readme/

* small changes to allow merging

* minor changes to format

* fixed up default readme

* added numpad and tweaked bottom row

* updated xd75 and preonic rev3 keymaps

* added initial half n half files

* fixed .h file

* updated names

* fixed layout in halfnhalf.h

* fixed manu name, changed bootloader in rules.mk

* removed redundancies in preonic and xd75 layouts

* readme updated