qmldom generates invalid XML if a string literal has escaped quotes

If a string literal has escaped quotes in it, `qmldom --dump-ast` generates invalid XML.

To reproduce, run `qmldom --dump-ast` on the following:

import QtQuick 6.3
Item {
    id: item
    property string name: "my \" name"
}
 

The result will have in its output:

<StringLiteral value="my \" name" literalToken="off:65 len:12 l:4 c:27 "> 

This will not be parseable as XML because this kind of escaping is illegal in XML.