Add support for HWP

[Rafiot]

There is a python library that can process HWP files, but it seems to be python2 only so I'm not sure how useful it will be but we should have a look at it at some point.

[dputtick]

Interesting, it also hasn't been updated in at least 2 years, which generally isn't a great sign. It would be great to support more non-western centric file formats.