feat/docx-field-codes

[erik-squared]

partition_docx() does not seem to render field codes embedded in the document as text in the output. For example, a document I am working with has the 'subject' property inserted liberally throughout the document, and this text vanishes in the output.

Ideally would like to have the property text rendered as part of output. I did find an old discussion in python_docx from years ago that discussed why this is difficult in general, but perhaps it can be solved for simpler cases such as document properties.

Not really a direct alternative, but perhaps it could be helpful to generate some type of indication that an element has been bypassed?