add 'i18n' to the rendering context dictionary description

Author: Alexander Smishlajev

roundup/cgi/templating.py

@@ -224,6 +224,10 @@ class in this file. If the tracker interfaces module defines a
     *false*
       Logical False value.
 
+    *i18n*
+      Internationalization service, providing string translation
+      methods ``gettext`` and ``ngettext``.
+
     """
     # construct the TemplatingUtils class
     utils = TemplatingUtils