Add OpenMSX deserialization test, fix issues

SabreTools.Models/OpenMSX/Software.cs

@@ -26,5 +26,17 @@ namespace SabreTools.Models.OpenMSX
 
         [XmlElement("dump")]
         public Dump[]? Dump { get; set; }
+
+        #region DO NOT USE IN PRODUCTION
+
+        /// <remarks>Should be empty</remarks>
+        [XmlAnyAttribute]
+        public XmlAttribute[]? ADDITIONAL_ATTRIBUTES { get; set; }
+
+        /// <remarks>Should be empty</remarks>
+        [XmlAnyElement]
+        public object[]? ADDITIONAL_ELEMENTS { get; set; }
+
+        #endregion
     }
 }