make everything more modular + basic kitagawa config using gnome

modules/desktop-environments/plasma6.nix

@@ -0,0 +1,17 @@
+{
+  config,
+  pkgs,
+  ...
+}: {
+  services.desktopManager.plasma6 = {
+    enable = true;
+    enableQt5Integration = true;
+  };
+
+  environment.plasma6.excludePackages = with pkgs.kdePackages; [
+    konsole
+    qrca
+  ];
+
+  services.displayManager.defaultSession = "plasma";
+}