more progress on custom options config

modules/components/display-managers/lightdm.nix

@@ -0,0 +1,11 @@
+{ inputs, self, ... }: {
+  flake.nixosModules.graphics = { config, pkgs, lib, ... }: {
+    config = lib.mkIf (config.components.displayManager == "lightdm") {
+      services.xserver.enable = true;
+      services.xserver.displayManager.lightdm = {
+        enable = true;
+        greeters.gtk.enable = true;
+      };
+    };
+  };
+}