refactor(de): move plasma config to separate file

modules/programs/plasma.nix

@@ -0,0 +1,15 @@
+{ pkgs, ... }:
+{
+  services = {
+    displayManager.sddm = {
+      enable = true;
+      wayland.enable = true;
+    };
+    desktopManager.plasma6.enable = true;
+  };
+
+  environment.plasma6.excludePackages = with pkgs.kdePackages; [
+    elisa
+    konsole
+  ];
+}