Added character limit for chat (#1586)

* Added character limit for chat

* Changed buffer reading from Int16 to Int32

Co-authored-by: Clément <clement.orlandini@gmail.com>

Content.Shared/Chat/ChatMaxMsgLengthMessage.cs

@@ -0,0 +1,39 @@
+using Lidgren.Network;
+using Robust.Shared.Interfaces.Network;
+using Robust.Shared.Network;
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Content.Shared.Chat
+{
+    /// <summary>
+    /// This message is sent by the server to let clients know what is the chat's character limit for this server.
+    /// It is first sent by the client as a request
+    /// </summary>
+    public sealed class ChatMaxMsgLengthMessage : NetMessage
+    {
+        #region REQUIRED
+
+        public const MsgGroups GROUP = MsgGroups.Command;
+        public const string NAME = nameof(ChatMaxMsgLengthMessage);
+        public ChatMaxMsgLengthMessage(INetChannel channel) : base(NAME, GROUP) { }
+
+        #endregion
+
+        /// <summary>
+        /// The max length a player-sent message can get
+        /// </summary>
+        public int MaxMessageLength { get; set; }
+
+        public override void ReadFromBuffer(NetIncomingMessage buffer)
+        {
+            MaxMessageLength = buffer.ReadInt32();
+        }
+
+        public override void WriteToBuffer(NetOutgoingMessage buffer)
+        {
+            buffer.Write(MaxMessageLength);
+        }
+    }
+}