Added AvaloniaUI project.

Harmonia.Core/Player/AudioPlayer.cs

@@ -36,6 +36,7 @@ public class AudioPlayer : IAudioPlayer
         {
             _playingSong = value;
             NotifyPropertyChanged(nameof(PlayingSong));
+            PlayingSongChanged?.Invoke(this, new());
         }
     }
 
@@ -111,6 +112,7 @@ public class AudioPlayer : IAudioPlayer
 
     protected virtual int PreviousSongSecondsThreshold => 5;
 
+    public event EventHandler? PlayingSongChanged;
     public event PropertyChangedEventHandler? PropertyChanged;
 
     public AudioPlayer(IAudioEngine audioEngine, IPlaylistRepository playlistRepository)