Make duplicate suffix inherent

SabreTools.DatItems/DatItem.cs

@@ -356,6 +356,12 @@ namespace SabreTools.DatItems
 
         #region Sorting and Merging
 
+        /// <summary>
+        /// Get unique duplicate suffix on name collision
+        /// </summary>
+        /// <returns>String representing the suffix</returns>
+        public virtual string GetDuplicateSuffix() => _internal.GetDuplicateSuffix();
+
         /// <summary>
         /// Get the dictionary key that should be used for a given item and bucketing type
         /// </summary>