Animate video playback modal in/out

Summary: Code written by Ashoat during video call explaining animations using the reanimated library.

Test Plan: Tested basic functionality on iOS. Will test media pipeline scenarios comprehensively after the remaining modal animation diffs.

Reviewers: ashoat, palys-swm

Reviewed By: ashoat

Subscribers: KatPo, zrebcu411, Adrian, subnub, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D721