move options back out to their config files, improve documentation

modules/features/applications/gui/nautilus.nix

@@ -1,4 +1,8 @@
 { inputs, self, ... }: {
+  imports = [ (inputs.helpers.mkMirroredModulesFlakeModule "graphicsOptions" ({ lib, ... }: {
+    options.features.applications.gui.nautilus.enable = lib.mkEnableOption "Nautilus";
+  })) ];
+
   flake.nixosModules.graphics = { pkgs, config, lib, ... }: {
     config = lib.mkIf (config.features.applications.gui.nautilus.enable) {
       environment.systemPackages = with pkgs; [