Add initial project structure and configuration files for Marechai.App

Marechai.App/Presentation/ShellViewModel.cs

@@ -0,0 +1,15 @@
+using Uno.Extensions.Navigation;
+
+namespace Marechai.App.Presentation;
+
+public class ShellViewModel
+{
+    private readonly INavigator _navigator;
+
+    public ShellViewModel(
+        INavigator navigator)
+    {
+        _navigator = navigator;
+        // Add code here to initialize or attach event handlers to singleton services
+    }
+}