Draft: [3.0] Added processing related to libvlc_MediaPlayerBuffering

This may improve UX.

let mediaPlayer: VLCMediaPlayer = ...
print(mediaPlayer.buffer)

For use with VLCMediaPlayerDelegate

// MARK: - VLCMediaPlayerDelegate
func mediaPlayerBufferChanged(_ aNotification: Notification) {
    guard let mediaPlayer = aNotification.object as? VLCMediaPlayer else { return }
    print(mediaPlayer.buffer)
}

func mediaPlayerStateChanged(_ aNotification: Notification) {
    guard let mediaPlayer = aNotification.object as? VLCMediaPlayer else { return }
    let currentState: VLCMediaPlayerState = mediaPlayer.state
        
    if (currentState == .buffering) {
        print(mediaPlayer.buffer)
    }
}

For use with NotificationCenter

NotificationCenter.default.addObserver(forName: VLCMediaPlayer.bufferChanged, object: nil, queue: .main) {
    guard let mediaPlayer = $0.object as? VLCMediaPlayer else { return }
    print(mediaPlayer.buffer)
}

For use with KVO

var bufferKVO: NSKeyValueObservation?
bufferKVO = mediaPlayer.observe(\.buffer) { mp, change in
    print(mp.buffer)
}

If this attempt is not suitable, please close this merge request.

best regards.