Add ClrMamePro deserialization test, fix issues

SabreTools.Models/ClrMamePro/ClrMamePro.cs

@@ -47,5 +47,12 @@ namespace SabreTools.Models.ClrMamePro
 
         /// <remarks>forcepacking</remarks>
         public string? ForcePacking { get; set; }
+
+        #region DO NOT USE IN PRODUCTION
+
+        /// <remarks>Should be empty</remarks>
+        public string[]? ADDITIONAL_ELEMENTS { get; set; }
+
+        #endregion
     }
 }