add initial marshmallow support

[stufisher]

Basic support for marshmallow schemas https://marshmallow.readthedocs.io/en/stable/

It would be nice if we could override the default renderer for these types of classes to show a table instead of the header style renderer?

[stufisher]

I would like to show inherited fields as well, however enabling inherited_members also shows all the methods inherited from the base marshmallow.Schema class. I added a blacklist to remove these methods / attributes, but there may be a cleaner way to deal with this that i am not seeing

[pawamoy]

Hi @stufisher, thanks a lot for your contributions, this is really appreciated 🙂

I'll review now!

[stufisher]

Thanks for reviewing, ill get back to you shortly with updates. Any idea on my second question about formatting via tables? I guess ill open an mkdocstrings ticket

[stufisher]

Sorry for the delays, think ive addressed the things youve mentioned :)

[pawamoy]

Hi again, no problem about the delays, I myself am having a hard time finding time/motivation to work on my open source projects in the evenings, after work 🙂 Thank you for getting back on this 🙂

I think this is good now, I'll squash and merge!