add operand property to allowed list (#17)

Author: karan-batavia

DotNetAstGen/SyntaxNodePropertiesResolver.cs

@@ -17,7 +17,7 @@ internal class SyntaxNodePropertiesResolver : DefaultContractResolver
             "Alias", "NamespaceOrType", "Arguments", "Expression", "Declaration", "ElementType", "Initializer", "Else",
             "Condition", "Statement", "Statements", "Variables", "WhenNotNull", "AllowsAnyExpression", "Expressions",
             "Modifiers", "ReturnType", "IsUnboundGenericName", "Default", "IsConst", "Parameters", "Types",
-            "ExplicitInterfaceSpecifier", "MetaData", "Kind", "AstRoot", "FileName", "Code"
+            "ExplicitInterfaceSpecifier", "MetaData", "Kind", "AstRoot", "FileName", "Code", "Operand"
         });
 
         private readonly List<string> _regexToAllow = new(new[]