Recursively parse an XML2 node tree into a `minixml` document

This uses 'xml2' package to do the parsing.

parse_inner(xml2_node, as_document = TRUE, as_pattern = FALSE)

Arguments

xml2_node	root node of a document or an element node
as_document	parse the root node as a document node. Default: TRUE
as_pattern	parse the root node as a pattern node. Default: FALSE