R1:959337ec62f5

Add crumbs to Calendar events to return to the month/day view

Summary: Ref T11326. This makes it a little easier to jump back up to check out your day.

Test Plan: {F1725575}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11326

Differential Revision: https://secure.phabricator.com/D16309