Add docs for enable_content_listener option.

Author: Ben Glassman

bundles/seo/configuration.rst

@@ -128,3 +128,16 @@ form_group
 
 The name of the form group of the group provided by the Sonata Admin
 Extension.
+
+``enable_content_listener``
+"""""""""""""""""""""""""""
+
+.. versionadded:: 1.2
+    The ``enable_content_listener`` configuration key was introduced in SeoBundle 1.2
+
+**type**: ``boolean`` **default**: ``true``
+
+Whether or not the ``Symfony\Cmf\Bundle\SeoBundle\EventListener\ContentListener`` should be loaded
+as a ``kernel.request`` listener. The ContentListener is responsible for extracting SEO data from
+CMF content documents. Set this to false to disable the listener. If you want to use your own content listener
+you will need to register your listener as a service and tag it as a ``kernel.request`` listener.