Fix #5236 [Translation] specify additional translation loading paths

Author: Pierre Maraitre

book/translation.rst

@@ -334,7 +334,7 @@ The translator service is accessible in PHP templates through the
 Translation Resource/File Names and Locations
 ---------------------------------------------
 
-Symfony looks for message files (i.e. translations) in the following locations:
+Symfony looks for message files (i.e. translations) in the following default locations:
 
 * the ``app/Resources/translations`` directory;
 
@@ -372,6 +372,18 @@ The choice of which loader to use is entirely up to you and is a matter of
 taste. The recommended option is to use ``xlf`` for translations.
 For more options, see :ref:`component-translator-message-catalogs`.
 
+.. note::
+
+    The the paths at which Symfony will look for message files can be modified by adding
+    your custom resources path in your config.yml:
+
+    .. code-block:: yml
+
+        framework:
+            translator:
+                paths:
+                    - %kernel.root_dir%/../vendor/Symfony/Component/Form/Resources/translations
+
 .. note::
 
     You can also store translations in a database, or any other storage by