These options will be used on objects of class 'xml_document'.
opts_xml_document(constructor = c("default", "next"), ..., simplify = TRUE)An object of class <constructive_options/constructive_options_xml_document>
Depending on constructor, we construct the object as follows:
"default" (default): We build the object using xml2::read_xml() or xml2::read_html()
on a string.
"next" : Use the constructor for the next supported class.