this is wrong, and I have made some changes already, but they were not uploaded... my bad 🤷

The `'extended_properties'` elements are now being parsed... although there is an ugly hack, basically, hardcoding what I want to get from the element (text) and from which element (eg. element[1[)

This implementation introduces a very hacky and ugly way of reading and writing to the document app.xml file, which is in charge of the extended properties.

extendedprops are now being properly populated.

still a very rough version, needs to be polished a just a tad bit more...