Create a CONTRIBUTING.md file

[leog]

I think it is crucial for any open source, quality project, with so much love put into it like this one, to have a CONTRIBUTING.md guide on how the open source community can chip in and match that love to organically help evolve a project.

I can jump in and propose some best practices but ideally, the people already working on the project should shape this guide with already established processes, so maybe this issue can help gather that info to then write the corresponding file? 👍