Support preventsDisplaySleepDuringVideoPlayback (#2019)

* Add flag on iOS

* Add flag in Android

* Add documentation

* Add changelog entry

* Also set setKeepScreenOn

* Fix prop not being set

* add preventsDisplaySleepDuringVideoPlayback to exoplayer

* Update android-exoplayer/src/main/java/com/brentvatne/exoplayer/ReactExoplayerView.java

* Update android-exoplayer/src/main/java/com/brentvatne/exoplayer/ReactExoplayerView.java

Co-authored-by: Jens Andersson <jens@fritan.com>

Co-authored-by: Anton Tanderup <antontandrup@gmail.com>
Co-authored-by: Jens Andersson <jens@fritan.com>