Add support for pytest.ini config

[tusharsadhwani]

Resolves #1

[leycec]

Unsurprisingly, this is superb. It's fascinating that config.getini() conveniently returns a pre-split list of strings already – probably thanks to the previously configured type='args' option, huh?

Thanks so much for the 0-day turnaround on this. I'm currently compiling the release notes for @beartype 0.17.0, which will push this use case when I introduce pytest-beartype. Please feel free to merge this whenever you like – and directly push whatever commits you like to the repository in the future. I implicitly trust everything you do. You're amazing... and you know it. 😉