Add fullscreen mode to Workboards

Summary: Cleans up Crumb Actions on Workboards. Adds fullscreen option. Fixes T6066

Test Plan:
Clicky Clicky. Test icon does not display on tablet, mobile.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T6066

Differential Revision: https://secure.phabricator.com/D15230