Docx Reader: Removed WithDState function

Replaced it with reader monad.

As far as I can tell the failing test is how it's meant to actually work? I can't see where I introduced a bug if not.

parPartsToInlines runs in the header, finds the anchor and adds the id to the headerMap. Later makeHeaderAnchor finds the span element whch parPartsToInlines leaves behind in the header, newIdenty becomes "anchor-header-1" as the anchor was already added in parPartsToInlines. Everything is renamed.