Added Whisper system for talking with players 2 tiles away. (#5994)

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Shared/Chat/ChatSelectChannel.cs

@@ -18,6 +18,11 @@ namespace Content.Shared.Chat
         /// </summary>
         Local = ChatChannel.Local,
 
+        /// <summary>
+        ///     Chat heard by players right next to each other
+        /// </summary>
+        Whisper = ChatChannel.Whisper,
+
         /// <summary>
         ///     Radio messages
         /// </summary>