previous method
Plays the previous video in the sequence.
Pauses the current video, moves to the previous one, and then starts playback.
Implementation
Future<void> previous() async {
currentController.pause();
_removePreviousListener();
_currentIndex =
(_currentIndex - 1 + controllers.length) % controllers.length;
currentController.seekTo(Duration(milliseconds: 0));
await Future.delayed(Duration(seconds: 1));
play();
}