add test requirements and pytest command

[woutdenolf]

This might be too specific so let me know if you have suggestions on how to generalize it.

I have several packages that supports this for testing

pip install ewokscore[test]
pytest --pyargs ewokscore

This PR adds a CLI option

grayskull pypi ewokscore --extras-require-test test

It then looks for "test" in extras_require to add requirements to the test section of the recipe.

In addition if "pytest" is in the test requirements it adds the command pytest --pyargs {name} to the test commands.

[marcelotrevisani]

Cool! Sorry for my delay I have beeing quite buse in the past weeks.
It looks good to me the general idea, I'm onboard with that. Just a few things that would be nice to add in this PR if you don't mind. Can you add a test for it please? it would be really cool if you add it to cover this new feature.
There is one failing test, I added two suggestions to the PR that will cover those cases, if you add any of them should be fine, the second one adding a new exception might be better as your current implementation you are using the try except block
but I am happy with either implementation :)

[woutdenolf]

When adding the test I realized it is cleaner to add the new feature to Configuration instead of CLIConfig.

[woutdenolf]

Sorry I didn't notice this project was using black. I'll fix that,

[marcelotrevisani]

there is just one failing test that need to be fixed, after that it should be good to go

[marcelotrevisani]

Cool! Thanks for your contribution! I will cut a new release after that