Add CI

[blopker]

Hey all, this PR adds some GitHub Action, uh, action.

Additions:

• main.yml: Runs unittests for the package only, no Django app. This is kept separate so we can install different packages/versions between integration and package tests. This runs the flake8 linter and tests with pytest. I also half added the black code formatter, but wanted to get feedback on if we want that before I actually reformat all the files. Do we want it? Should we format all files, or just the package?
• chat.yml: Runs unittests and integration tests for the chat app. The tests are just placeholders and the only integration test is to run curl against the index page to show the server started correctly. I assume we'll replace that with something more useful.

These both run in parallel so it all happens pretty fast.

Everything works so far, but none of the tests are very useful right now. We need to add some good ones! This is just a start, something to start the discussion around.

Cheers!

[blopker]

Thanks for the feedback! Yes, the Python version I picked was arbitrary (latest - 1). I'm glad this started the discussion around what we should support. Right now I'm hearing Django 3.1+ and Python 3.6+ which is fine by me. Django 3.2 will be an LTS release and we should consider only supporting that plus newer once it comes out.

I don't agree with everything black does, but I'm generally more interested in the consistency it provides so I would love to add it. I'll actually activate it in another PR so the formatting changes don't affect this PR.

As for tox, GitHub Actions has matrix testing built in if we want to test multiple versions of things so I think we'd only use it for local testing. That can certainly get added later though.

I'm going to merge this now so we can get some testing started, I'll do a followup with black and the right Python version.

Thanks!