feat: setup demo.

src/Ursa/Controls/Dialog/OverlayDialogManager.cs

@@ -0,0 +1,23 @@
+using System.Collections.Concurrent;
+
+namespace Ursa.Controls;
+
+internal static class OverlayDialogManager
+{
+    private static ConcurrentDictionary<string, OverlayDialogHost> _hosts = new();
+    
+    public static void RegisterOverlayDialogHost(OverlayDialogHost host, string id)
+    {
+        _hosts.TryAdd(id, host);
+    }
+    
+    public static void UnregisterOverlayDialogHost(string id)
+    {
+        _hosts.TryRemove(id, out _);
+    }
+    
+    public static OverlayDialogHost? GetOverlayDialogHost(string id)
+    {
+        return _hosts.TryGetValue(id, out var host) ? host : null;
+    }
+}