New: Darkmode (#3039)

* New: Native Theme Engine

Co-Authored-By: Zak Saunders <thezak48@users.noreply.github.com>
(cherry picked from commit 2291f3e00eb2ff9268a0b2f49da8dde82ee13c04)

* Update CSS for themes

Co-authored-by: Qstick <qstick@gmail.com>

frontend/postcss.config.js

@@ -1,7 +1,6 @@
 const reload = require('require-nocache')(module);
 
 const cssVarsFiles = [
-  './src/Styles/Variables/colors',
   './src/Styles/Variables/dimensions',
   './src/Styles/Variables/fonts',
   './src/Styles/Variables/animations',