add signalr support

NoteHub.cs

@@ -0,0 +1,22 @@
+using BinaryDad.Notes.Services;
+using Microsoft.AspNetCore.SignalR;
+
+namespace BinaryDad.Notes
+{
+    public class NoteHub : Hub
+    {
+        private readonly INoteService noteService;
+
+        public NoteHub(INoteService noteService)
+        {
+            this.noteService = noteService;
+        }
+
+        public async Task SaveNote(string content)
+        {
+            noteService.Save(content);
+
+            await Clients.Others.SendAsync("updateNote", content);
+        }
+    }
+}