Documenting the new method addNormalizer in OptionsResolver component

Author: yceruto

components/options_resolver.rst

@@ -437,6 +437,14 @@ if you need to use other options during normalization::
         }
     }
 
+.. versionadded:: 4.3
+
+    To normalize a new allowed value in sub-classes that is being normalized
+    in parent classes use :method:`Symfony\\Component\\OptionsResolver\\OptionsResolver::addNormalizer`.
+    This way, the ``$value`` argument will receive the previously normalized
+    value, otherwise you can prepend the new normalizer by passing ``true`` as
+    third argument.
+
 Default Values that Depend on another Option
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~