Add listrom deserialization test, fix issues

SabreTools.Models/Listrom/Dat.cs

@@ -0,0 +1,14 @@
+namespace SabreTools.Models.Listrom
+{
+    public class Dat
+    {
+        public Set[]? Set { get; set; }
+
+        #region DO NOT USE IN PRODUCTION
+
+        /// <remarks>Should be empty</remarks>
+        public string[]? ADDITIONAL_ELEMENTS { get; set; }
+
+        #endregion
+    }
+}