create a setup builder impl from MicaSetup

Build/MicaSetup/Design/Controls/Shell/ShellControl.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Windows;
+using System.Windows.Controls;
+
+namespace MicaSetup.Design.Controls;
+
+public class ShellControl : ContentControl
+{
+    public string Route
+    {
+        get => (string)GetValue(RouteProperty);
+        set => SetCurrentValue(RouteProperty, value);
+    }
+
+    public static readonly DependencyProperty RouteProperty = DependencyProperty.Register(nameof(Route), typeof(string), typeof(ShellControl), new(string.Empty));
+
+    public ShellControl()
+    {
+        Routing.Shell = new WeakReference<ShellControl>(this);
+        FocusVisualStyle = null!;
+        Loaded += (_, _) => Routing.GoTo(Route);
+    }
+}