When adding a new playlist, prompt user for the playlist name.

Harmonia.WinUI/ViewModels/PlaylistDetailViewModel.cs

@@ -473,7 +473,17 @@ public partial class PlaylistDetailViewModel : ViewModelBase
 
     private async Task NewPlaylistAsync(CancellationToken cancellationToken)
     {
+        string playlistName = await _messageService.InputTextAsync(
+            $"New Playlist",
+            "Enter a new name for the playlist:",
+            "New Playlist");
+
+        if (string.IsNullOrWhiteSpace(playlistName))
+            return;
+
         Playlist playlist = await _playlistManager.AddPlaylistAsync();
+        playlist.SetName(playlistName);
+
         _playlistManager.CurrentPlaylist = playlist;
     }