Add multi-layer in-hand and clothing support (#6740)

Content.Client/Inventory/ClientInventoryComponent.cs

@@ -30,6 +30,12 @@ namespace Content.Client.Inventory
         [ViewVariables]
         [DataField("speciesId")] public string? SpeciesId { get; set; }
 
+        /// <summary>
+        ///     Data about the current layers that have been added to the players sprite due to the items in each equipment slot.
+        /// </summary>
+        [ViewVariables]
+        public readonly Dictionary<string, HashSet<string>> VisualLayerKeys = new();
+
         public bool AttachedToGameHud;
     }
 }