Modify admin chat (#13050)

* split admin chat into new channel

* add ability to play audio when a chat message is received and add audio to admin chat

* give client control of AdminChat sound and volume + suppress sound for senders

Content.Shared/Chat/ChatChannel.cs

@@ -60,14 +60,19 @@ namespace Content.Shared.Chat
         Dead = 1 << 9,
 
         /// <summary>
-        ///     Admin chat
+        ///     Misc admin messages
         /// </summary>
         Admin = 1 << 10,
 
+        /// <summary>
+        ///     Admin chat
+        /// </summary>
+        AdminChat = 1 << 11,
+
         /// <summary>
         ///     Unspecified.
         /// </summary>
-        Unspecified = 1 << 11,
+        Unspecified = 1 << 12,
 
         /// <summary>
         ///     Channels considered to be IC.