Initial Client/Server Communication

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

Assets/Scripts/MessagePack/Resolvers/CachingFormatterResolver.cs

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+// Copyright (c) All contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using MessagePack.Formatters;
+using MessagePack.Internal;
+
+namespace MessagePack.Resolvers
+{
+    /// <summary>
+    /// A base class for <see cref="IFormatterResolver"/> classes that want to cache their responses for perf reasons.
+    /// </summary>
+    internal abstract class CachingFormatterResolver : IFormatterResolver
+    {
+        /// <summary>
+        /// The cache of types to their formatters.
+        /// </summary>
+        private readonly ThreadsafeTypeKeyHashTable<IMessagePackFormatter> formatters = new ThreadsafeTypeKeyHashTable<IMessagePackFormatter>();
+
+        /// <inheritdoc />
+        public IMessagePackFormatter<T> GetFormatter<T>()
+        {
+            if (!this.formatters.TryGetValue(typeof(T), out IMessagePackFormatter formatter))
+            {
+                formatter = this.GetFormatterCore<T>();
+                this.formatters.TryAdd(typeof(T), formatter);
+            }
+
+            return (IMessagePackFormatter<T>)formatter;
+        }
+
+        /// <summary>
+        /// Looks up a formatter for a type that has not been previously cached.
+        /// </summary>
+        /// <typeparam name="T">The type to be formatted.</typeparam>
+        /// <returns>The formatter to use, or <c>null</c> if none found.</returns>
+        protected abstract IMessagePackFormatter<T> GetFormatterCore<T>();
+    }
+}