#639 added copywrite notice (#648)

src/Ocelot/WebSockets/Middleware/WebSocketsProxyMiddleware.cs

@@ -1,3 +1,7 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+// Modified https://github.com/aspnet/Proxy websockets class to use in Ocelot.
+
 using System;
 using System.Linq;
 using System.Net.WebSockets;