1.60.0
(feat): Add XML support for xml-encoded object types (e.g. TwiML). Generated types gain
ToXml()/ToXmlElement(), <Type>FromXml(string)/<Type>FromXmlElement(...),
fluent child builders (e.g. response.Say(...), Add-prefixed on collision), and
ExtraAttributes/ExtraChildren to round-trip unknown attributes and elements.
A standard-library core/xml.go runtime is emitted only when xml-encoded types exist.