Add CI to validate code style

[pombredanne]

And also run black on all the code including etc

[keshav-space]

So @pombredanne we need to have black in setup.cfg
https://github.com/nexB/skeleton/blob/4004ebe15cd83b152acc124808231e63f91fbf10/setup.cfg#L38-L41
And a test_skeleton_codestyle.py under tests/
Is that good enough?

[pombredanne]

@keshav-space

we need to have black in setup.cfg

Yes!

And a test_skeleton_codestyle.py under tests/ Is that good enough?

The skeleton being a template, we have to think a minute about the tests... They will be merged in repos using the skeleton... and at the same we want them to run on the skeleton proper.
Therefore test_skeleton_codestyle.py or some other name must be designed to be unique across all projects.
This looks like a good conspicuous and unique name, so go for it!
👍