Play a sound when receiving a new chat message
Summary:
Ref T7567. Nothing fancy yet, just getting this working. Sound is lightly edited version of "Pop 6":
https://www.freesound.org/people/greenvwbeetle/sounds/244656/
Test Plan: Sent chat, heard sounds.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T7567
Differential Revision: https://secure.phabricator.com/D17721