Added playlist view and initial playlist view logic.

Harmonia.UI/App.axaml.cs

@@ -3,6 +3,7 @@ using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.Markup.Xaml;
 using Harmonia.Core.Extensions;
+using Harmonia.UI.Caching;
 using Harmonia.UI.ViewModels;
 using Harmonia.UI.Views;
 using Microsoft.Extensions.DependencyInjection;
@@ -22,6 +23,9 @@ public partial class App : Application
         services.AddSingleton<MainWindow>();
         services.AddSingleton<PlaybackBarViewModel>();
         services.AddSingleton<PlayingSongInfoViewModel>();
+        services.AddSingleton<PlaylistViewModel>();
+
+        services.AddSingleton<IAudioBitmapCache, AudioBitmapCache>();
 
         services.AddHarmonia();