xml.stringify( `obj` ) should not alter `obj`

[inverted-capital]

If I do:

        const withRoot = Object.freeze({ [tagName]: json })
        const snippet = xml.stringify(withRoot)

And error will be thrown:

error: TypeError: Cannot add property ~name, object is not extensible
  ;(document as Record<PropertyKey, unknown>)["~name"] ??= "xml"
                                                      ^
    at xml_prolog (https://jsr.io/@libs/xml/6.0.4/stringify.ts:135:55)
    at Module.stringify (https://jsr.io/@libs/xml/6.0.4/stringify.ts:74:11)

In general, an operation to translate one object into another should not alter the source object.

(thank you for this library - it is the best xml parser out there)