[Keymap] Add vim-style keymap for lets split (#5399)

[Keymap] Add vim-style keymap for lets split (#5399)

* initial commit

* initial commit

* fixed indents

* spelling, capitalization, and order.

* added dota mode keymap, removed old comments

* fixed default keymap always having tilde, instead of grave accent and tilde. Improved dota keymap.

* lower does not change backspace to delete anymore

* corrected pgup/pgdown

* changed period on lower from numpad dot to regular dot

* added colemak and dvorak

* made colemak/dvorak border keys consistent with querty

* updated to match current practices, added custom metakeys for dvorak and colemak

* added disclaimer about audio

* renamed to lowercase

* replaced include guards with #pragma once

Co-Authored-By: rileyweber13 <rileyw13@protonmail.com>
* removed unncessary include

Co-Authored-By: rileyweber13 <rileyw13@protonmail.com>
* removed defines included in core

Co-Authored-By: rileyweber13 <rileyw13@protonmail.com>
* replace defines with an enum, switched from custom function to set_single_persistent_default_layer

* removed ifndef/include/endif left over from previous build system

* removed unnecessary ifdef block

* updated soungs to work with set_single_persistent_default_layer