Add kde plasma

hosts/common/optional/desktop/plasma.nix

@@ -0,0 +1,15 @@
+{pkgs, ...}: {
+  imports = [./global.nix ./x11.nix];
+
+  services.xserver.desktopManager.plasma5.enable = true;
+  environment.plasma5.excludePackages = with pkgs.libsForQt5; [
+    elisa
+    gwenview
+    okular
+    oxygen
+    khelpcenter
+    konsole
+    plasma-browser-integration
+    print-manager
+  ];
+}