Disable chat for the first 5s (configurable) after joining a server.

OpenRA.Game/Server/Connection.cs

@@ -31,6 +31,7 @@ namespace OpenRA.Server
 		public readonly int PlayerIndex;
 		public readonly string AuthToken;
 		public readonly EndPoint EndPoint;
+		public readonly Stopwatch ConnectionTimer = Stopwatch.StartNew();
 
 		public long TimeSinceLastResponse => Game.RunTime - lastReceivedTime;