feat: add splash window.

demo/Sandbox/App.axaml.cs

@@ -1,4 +1,5 @@
 using Avalonia;
+using Avalonia.Controls;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.Markup.Xaml;
@@ -21,10 +22,7 @@ public partial class App : Application
             // Line below is needed to remove Avalonia data validation.
             // Without this line you will get duplicate validations from both Avalonia and CT
             BindingPlugins.DataValidators.RemoveAt(0);
-            desktop.MainWindow = new MainWindow
-            {
-                DataContext = new MainWindowViewModel(),
-            };
+            desktop.MainWindow = new MainSplashWindow();
         }
 
         base.OnFrameworkInitializationCompleted();