Add ClrMamePro deserialization test, fix issues

SabreTools.Models/ClrMamePro/BiosSet.cs

@@ -1,7 +1,7 @@
 namespace SabreTools.Models.ClrMamePro
 {
     /// <remarks>biosset</remarks>
-    public class BiosSet
+    public class BiosSet : ItemBase
     {
         /// <remarks>name</remarks>
         public string Name { get; set; }
@@ -11,5 +11,12 @@ namespace SabreTools.Models.ClrMamePro
 
         /// <remarks>default</remarks>
         public string? Default { get; set; }
+
+        #region DO NOT USE IN PRODUCTION
+
+        /// <remarks>Should be empty</remarks>
+        public string[]? ADDITIONAL_ELEMENTS { get; set; }
+
+        #endregion
     }
 }