add skeleton NowPlayingHub

Selector.Web/Hubs/NowPlayingHub.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.SignalR;
+
+using Selector.Cache;
+
+namespace Selector.Web.Hubs
+{
+    public interface INowPlayingHubClient
+    {
+        public Task OnNewPlaying(CurrentlyPlayingDTO context);
+    }
+
+    public class NowPlayingHub: Hub<INowPlayingHubClient>
+    {
+        public Task SendNewPlaying(CurrentlyPlayingDTO context)
+        {
+            return Clients.All.OnNewPlaying(context);
+        }
+    }
+}