Shrink packet header size

MistoxServer/mPacket/PacketAttribute.cs

@@ -0,0 +1,13 @@
+using System;
+
+namespace MistoxServer.Attributes {
+    
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, Inherited = false, AllowMultiple = false)]
+    public sealed class mPacket : Attribute {
+        public byte ID { get; }
+        public mPacket(byte id) {
+            ID = id;
+        }
+    }
+
+}