📦 Created config files with common code

- Created common.nix for various configs
- Created theme.nix for theme related configs
- Moved some code to more logical files
- Moved some standalone files into nix multiline strings, in order to
  inject data

modules/locale.nix

@@ -5,6 +5,7 @@ let
   utf-8 = "UTF-8";
   en = "en_GB.${utf-8}";
   nb = "nb_NO.${utf-8}";
+  common = import ../common.nix;
 in
 {
   # Configure console keymap
@@ -31,10 +32,7 @@ in
   };
 
   # Configure keymaps
-  services.xserver.xkb = {
-    layout = "gb,no";
-    options = "grp:alt_shift_toggle"; # Toggle using ALT + SHIFT
-  };
+  services.xserver.xkb = common.keymaps;
 
   # Set your time zone.
   time.timeZone = "Europe/Oslo";