Add method to read form data

[morungos]

A second common use case, added by request in Text::Extract::Word, was to read form data from protected Word files. Again, the code for this still exists in the Perl component, but we should port it here.

[ArmorDarks]

Any plans to add it?

[morungos]

We can now read direct from a buffer as per #11, so that should be sufficient for that. The form data issue is bigger, as it is essentially about parsing Word fields, which is another low-level data feature. This remains something I will look at when I get an opportunity or resourcing.