Create Contributing guide information

[lawik]

Capturing automated checks that people can expect as well as actually trying to capture conventions and practices that are expected.

[lawik]

@fhunleth I know you have more and you might have opinions on what I included. Just edit away. I wanted to get this started but I don't think I can finish it without input. And I suppose there are just a few items and a couple of minutes to bang this out. Then we can look at making Credo plugins or something :)

[fhunleth]

@lawik I think this is great, but your PR reminded me that we already have a contributing guide. I hadn't looked at it in a really long time and feel that it's not only out of date now, but also missing some new things that you added. Here's a link to the old guide. https://github.com/nerves-project/.github/blob/main/CONTRIBUTING.md. Let me know if you think it's best to refresh it or do something else.

[lawik]

This document could be changed to be a coding-standards one. That Contributing guide is kind of wide and isn't the best thing to link someone who is in the midst of contributing code. The other one may also need some review but seems good overall :)

It mentions a Nerves Radar, is that a thing and is it relevant for outside contributors to know?

[fhunleth]

It mentions a Nerves Radar, is that a thing and is it relevant for outside contributors to know?

Oh gosh. That needs to be deleted.

I was under the impression that the CONTRIBUTING.md guide would appear in the GitHub UI somewhere, but it doesn't seem to. Maybe we delete the whole thing and go with yours. I would like it to be discoverable on all Nerves-related projects. Perhaps we should move the discussion to Discord since you uncovered something that's going to hit every repository.