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