minor #21331 Add documentation for extending IsGranted attribute (tcoch)

This PR was squashed before being merged into the 7.4 branch.

Discussion
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 Add documentation for extending `IsGranted` attribute

This PR adds documentation related to new feature symfony/symfony#61542
It will close issue #21326

Commits
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eccf50a  Add documentation for extending `IsGranted` attribute

Author: xabbuh

security.rst

@@ -2523,6 +2523,26 @@ that is thrown with the ``exceptionCode`` argument::
         // ...
     }
 
+You can also extend the ``IsGranted`` attribute to create meaningful shortcuts::
+
+    // src/Security/Attribute/IsAdmin.php
+    // ...
+
+    use Symfony\Component\Security\Http\Attribute\IsGranted;
+
+    class IsAdmin extends IsGranted
+    {
+        public function __construct()
+        {
+            return parent::__construct('ROLE_ADMIN');
+        }
+    }
+
+.. versionadded:: 7.4
+
+    The :class:`Symfony\\Component\\Security\\Http\\Attribute\\IsGranted`
+    attribute is extendable since Symfony 7.4.
+
 .. _security-template:
 
 Access Control in Templates