Initial Client/Server Communication

#1
Followed the MagicOnion quickstart guide, borrowing code from the chat sample app to get something working

Assets/Scripts/MagicOnion.Unity/ChannelExtensions.cs

@@ -0,0 +1,19 @@
+using Grpc.Core;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace MagicOnion
+{
+    public static class ChannelExtensions
+    {
+        /// <summary>
+        /// Safety way for subscribe streaming events.
+        /// </summary>
+        public static void RegisterStreamingSubscription(this Channel channel, IDisposable subscription)
+        {
+            channel.ShutdownToken.Register(() => subscription.Dispose());
+        }
+    }
+}