📦 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/security.nix

@@ -23,7 +23,7 @@
   };
 
   services = {
-    pcscd.enable = true;
+    pcscd.enable = true; # Required for Yubikey
     udev.packages = with pkgs; [ yubikey-personalization ];
   };
 }