Add filing parsing packages to README

[mrx23dot]

In the readme please suggest a good XML SEC parsing python library.

(some guidance for new users where to go next)

[jadchaar]

Hi @mrx23dot, which filings are you looking to parse?

[mrx23dot]

10-K, but I guess a universal parser would be nice to be linked.

[jadchaar]

I'd have to do some research into packages dedicated to parsing, but I know of an R package called quantmod that is pretty widely used: https://cran.r-project.org/web/packages/quantmod/index.html.