fix(RCTVideo.swift): add audiovisualBackgroundPlaybackPolicy when pla…

[Dawqss]

Summary of Changes

• Fixed iOS background playback behavior:
  Added logic to set audiovisualBackgroundPlaybackPolicy on the player instance to ensure video continues playing when the app goes into the background.

if (_playInBackground) {
    _player!.audiovisualBackgroundPlaybackPolicy = .continuesIfPossible
} else {
    _player!.audiovisualBackgroundPlaybackPolicy = .automatic
}

• Without this, iOS would consistently pause video playback when the app was backgrounded, even if background playback was expected.

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How to test:

Just play any video with react-native-video player and go to background, video should pause

Motivation

Video stopped playing in background mode even though playInBackground was set to true.

[KrzysztofMoch]

Thank you for PR!
Our current min version of iOS is 13.0, but this property is 15.0+ (from what I can see in docs). Can you add version availability check? Thanks!

[KrzysztofMoch]

Thanks!