Contributor instructions for testing and style

[drcandacemakedamoore]

There is no obvious developer's documentation. The contributing.md would be fine except does not cover certain issues i.e. testing and linting. Many people may want to tinker with what you have done, and hopefully even contribute to the package. I am looking for documentation somewhere that tells people how to run the testing, so they can test new stuff before sending it. I eventually say some notes on contributing, somewhere. This could be in a more obvious place i.e. linked off the README, but the contributing.md is also fine as a stand-alone. Just a few more details please.

[alexzwanenburg]

Thanks for the feedback!

I will add instructions on style and testing to contributing.md, and link that file in README.md.

openjournals/joss-reviews#6413