add the syncthing service

modules/nixOS/default.nix

@@ -58,6 +58,13 @@ in {
     sharedSettings = {
       # put settings here that are shared between homemanager and nixos, e.g.
       # hyprland.enable = lib.mkEnableOption "enable hyprland";
+
+      mainUser = lib.mkOption {
+        type = lib.types.str;
+        default = "prunebutt";
+        example = "mainUser";
+        description = "The main user that runs the system";
+      };
     };
   };