Add support of new param - federated_domain_name

Change-Id: I6e6555a4189b4e9855dc160dd8defef848e7352f
diff --git a/README.rst b/README.rst
index bf5ceeb..6a247c8 100644
--- a/README.rst
+++ b/README.rst
@@ -319,6 +319,7 @@
           protocol: saml2
           remote_id_attribute: Shib-Identity-Provider
           federation_driver: keystone.contrib.federation.backends.sql.Federation
+          federated_domain_name: Federated
           trusted_dashboard:
             - http://${_param:proxy_vip_address_public}/horizon/auth/websso/
           shib_url_scheme: https