setPlaybackRate method
Sets the playback rate - call this after first calling play() or resume().
iOS and macOS have limits between 0.5 and 2x Android SDK version should be 23 or higher
Implementation
Future<void> setPlaybackRate(double playbackRate) async {
_playbackRate = playbackRate;
await creatingCompleter.future;
return _platform.setPlaybackRate(playerId, playbackRate);
}