Add nionutils project (strict typing).

[cmeyer]

I'm not sure this is ready for merging yet - I thought the PR would run the tests.

The question is whether the mypy command runs from within the cloned directory or from the directory above?

[hauntsaninja]

It runs within the cloned directory. mypy_primer CI doesn't run mypy_primer, because you'd effectively need a mypy_primer_primer to get reasonable output :-)

[cmeyer]

Ok this should be ready to go.

[hauntsaninja]

Thanks!