Feature Request: Add support for "strict" format

[Spectre5]

It would be great if the strict format was supported for docx/docm files. I think it basically just requires different ns tags to be used. Here are the tags used in a similar project, mammoth. It does not include as many tags as in docx2python though, so I'm not totally sure what the strict format tags are for some of the other tags used in this libraries file namespace.py.

If you have a file that includes all of the tags for this library, then you could save it in strict format to see what those tags become.