Add information about how to contribute to PyLadies

[marimeireles]

@sleepypioneer started an amazing document on how to contribute to our community.
Reading this doc I realized it could be useful to many others! So we'd like to add it to our page.

Here's the doc: https://docs.google.com/document/d/1oT_eTbBcPmurHcHQJDlcyq5RwXeoABXiA7azp7zq_PM/edit#heading=h.xmte97fhh0zh

Feel free to ask questions.

[sleepypioneer]

This now exists at https://berlin.pyladies.com/community-organisation/intro.html we just need to link the two websites and maybe think about them both eventually have the same look and feel