Initial Client/Server Communication

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

Assets/Scripts/MessagePack/Internal/DateTimeConstants.cs

@@ -0,0 +1,14 @@
+// Copyright (c) All contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+
+namespace MessagePack.Internal
+{
+    internal static class DateTimeConstants
+    {
+        internal const long BclSecondsAtUnixEpoch = 62135596800;
+        internal const int NanosecondsPerTick = 100;
+        internal static readonly DateTime UnixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+    }
+}