6.0.0

• Raised the minimum required Node.js version to ^22.22.2 || ^24.15.0 || >=26.0.0.
• Fixed serialization to reject invalid XML characters in attribute values, including namespace declaration values, when requireWellFormed is enabled.
• Fixed stack overflows in XML character validation for large strings.
• Fixed a TypeError when serializing namespaces named constructor, toString, or __proto__. (#33)
• Fixed confusion between the null namespace and a namespace named "null", which could change an element's namespace or cause false duplicate-attribute errors.
• Fixed namespace prefix declarations leaking between sibling elements, which could produce undeclared prefixes.