decreaseVolume method
Decrease volume between 0.0 - 1.0, 0.0 being mute and 1.0 full volume.
Implementation
Future<void> decreaseVolume(double decreaseBy) async {
final currentVolume = _videoPlayerController?.value.volume ?? 0;
final volumeAfterDecrease = currentVolume - decreaseBy;
final volume = _verifyVolumeBounds(volumeAfterDecrease);
await setVolume(volume);
_flickManager._handleVolumeChange(volume: volume);
}