Added SinaglR

Server/Hubs/NotificationHub.cs

@@ -0,0 +1,12 @@
+using Barcode.Host.Shared.Models;
+using Microsoft.AspNetCore.SignalR;
+
+namespace Barcode.Host.Server.Hubs;
+
+public class NotificationHub : Hub
+{
+
+    public async Task NotifyAll(Notification notification) =>
+        await Clients.All.SendAsync(nameof(NotifyAll), notification);
+
+}