Updated certain events to have more concrete event arguments. Added try-catch block around playlist save logic. Added DispatchQueue where necessary.

Harmonia.Core/Player/PlayingSongChangedEventArgs.cs

@@ -0,0 +1,9 @@
+using Harmonia.Core.Playlists;
+
+namespace Harmonia.Core.Player;
+
+public class PlayingSongChangedEventArgs(PlaylistSong? oldSong, PlaylistSong? newSong) : EventArgs
+{
+    public PlaylistSong? OldSong { get; } = oldSong;
+    public PlaylistSong? NewSong { get; } = newSong;
+}