NEW: tutorial/how-to guide for new developers looking to contribute to the rachis ecosystem #180

We currently have a gap in our contribution section for new developers who want to contribute to the rachis ecosystem. I'm imagining this tutorial would start with something like:

• I'm a new developer and I'd like to contribute, where do I start?

This tutorial could go through how to pick a suitable issue to tackle (ie utilizing the good-first-issue label), and then all of the guidelines and/or best practices we have for contributions. Things like how we recommend structuring PRs (ie granular commits are helpful, keeping code changes within the scope of the issue, using flake8 for formatting, etc), our PR template & prefixes, and then some basic info about our code review process and/or what to expect when CI is passing/failing.

I think this would be a nice thing for new developers both inside and outside of our team(s) to utilize - this could be a nice onboarding tutorial for any new undergrads or devs we hire internally in addition to the greater dev community.