Update documentation.

Resources/doc/reference/templates.rst

@@ -48,6 +48,7 @@ Usage of each template :
 * show : the template to use for the show action
 * edit : the template to use for the edit and create action
 * history : the template to use for the history / audit action
+* history_revision_timestamp : the template to use when rendering the timestamp of a given revision
 * list_block : the template used for the list of admin blocks on the dashboard
 * preview : the template to use for previewing an edit / create action
 * short_object_description: used to represent the entity in one-to-one/many-to-one relations
@@ -102,4 +103,4 @@ Row Template
 
 It is possible to completely change how each row of results is rendered in the
 list view. For more information about this, see the :doc:`recipe_row_templates`
-cookbook entry.
+cookbook entry.