sinb-box mux add padding option

https://github.com/2dust/v2rayN/issues/5544

v2rayN/ServiceLib/Handler/CoreConfig/CoreConfigSingbox.cs

@@ -702,6 +702,7 @@ namespace ServiceLib.Handler.CoreConfig
                         enabled = true,
                         protocol = _config.mux4SboxItem.protocol,
                         max_connections = _config.mux4SboxItem.max_connections,
+                        padding = _config.mux4SboxItem.padding,
                     };
                     outbound.multiplex = mux;
                 }

v2rayN/ServiceLib/Models/ConfigItems.cs

@@ -202,6 +202,7 @@
     {
         public string protocol { get; set; }
         public int max_connections { get; set; }
+        public bool? padding { get; set; }
     }
 
     [Serializable]

v2rayN/ServiceLib/Models/SingboxConfig.cs

@@ -150,6 +150,7 @@
         public bool enabled { get; set; }
         public string protocol { get; set; }
         public int max_connections { get; set; }
+        public bool? padding { get; set; }
     }
 
     public class Utls4Sbox