added a tip to register annotations namespaces

Author: Noel Garcia

components/validator/resources.rst

@@ -124,6 +124,21 @@ To disable the annotation loader after it was enabled, call
     In order to use the annotation loader, you should have installed the
     ``doctrine/annotations`` and ``doctrine/cache`` packages from `Packagist`_.
 
+.. tip::
+
+    Remember that annotation classes aren't loaded automatically, so you should load 
+    them like Symfony usually does in the ``app/autoload.php`` file::
+    
+        use Composer\Autoload\ClassLoader;
+        use Doctrine\Common\Annotations\AnnotationRegistry;
+
+        /** @var ClassLoader $loader */
+        $loader = require __DIR__.'/../vendor/autoload.php';
+        
+        AnnotationRegistry::registerLoader([$loader, 'loadClass']);
+        
+        return $loader;
+
 Using Multiple Loaders
 ----------------------