Split common and GUI code into separate projects

RedBookPlayer.GUI/App.xaml.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Diagnostics;
+using System.IO;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.ApplicationLifetimes;
+using Avalonia.Markup.Xaml;
+using RedBookPlayer.GUI;
+
+namespace RedBookPlayer
+{
+    public class App : Application
+    {
+        public static Settings Settings;
+
+        static App() =>
+            Directory.SetCurrentDirectory(Path.GetDirectoryName(Process.GetCurrentProcess().MainModule.FileName));
+
+        public override void Initialize()
+        {
+            AppDomain.CurrentDomain.UnhandledException += (e, f) =>
+            {
+                Console.WriteLine(((Exception)f.ExceptionObject).ToString());
+            };
+
+            AvaloniaXamlLoader.Load(this);
+        }
+
+        public override void OnFrameworkInitializationCompleted()
+        {
+            if(ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
+            {
+                desktop.MainWindow   = new MainWindow();
+                desktop.ShutdownMode = ShutdownMode.OnMainWindowClose;
+
+                Settings = Settings.Load("settings.json");
+            }
+
+            base.OnFrameworkInitializationCompleted();
+        }
+    }
+}