add validation of registeration form

app/Http/Controllers/Auth/RegisterController.php

@@ -46,6 +46,7 @@ class RegisterController extends Controller
     protected function validator(array $data)
     {
         return Validator::make($data, [
+            'marking' => 'required|max:255|unique:markings'
             'email' => 'required|email|max:255|unique:users',
             'password' => 'required|min:6|confirmed',
         ]);