Summary: Ref T7951, Starting the Calendar user guide
Test Plan: Go to {nav Diviner > Phabricator User Docs > Calendar User Guide}, read about how fabulous the Calendar application is.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: epriestley, Korvin
Maniphest Tasks: T7951
Differential Revision: https://secure.phabricator.com/D13496
