[native] Play button for video messages
Summary: Added play button for video messages
Test Plan: Looked fine on iOS Simulator: https://blob.sh/atul/comm-play-button.png
Reviewers: ashoat, palys-swm
Reviewed By: ashoat
Subscribers: KatPo, zrebcu411, Adrian, subnub
Differential Revision: https://phabricator.ashoat.com/D834