Add pre-commit for code linting

[altheaden]

This PR adds pre-commit for automatic code linting. I've also added pre-commit to the CI build workflow to automatically lint any incoming PRs.

I'm including changes that will satisfy all pre-commit hooks except flake8. The changes flake8 wants require manual editing to many code files, so we're opting to only deal with those issues on a file-by-file basis as new changes come in. Because of this, the linting step of CI for this PR will fail, but that's expected.

Finally, I'm including a small bugfix to the docs CI workflow.

[altheaden]

@xylar isort reordering the imports for this file broke everything, so I've excluded it here.

[xylar]

Let's follow up on that in a separate PR. We don't need all the __future__ stuff anymore. That was for python 2. Maybe that will help. But if that's not the problem, we maybe need to add missing imports somewhere else.

[xylar]

Let's exclude this file from pre-commit checks because I just added a test in #220 to make sure it's formatted as expected and the two might slightly disagree. In particular, the json output seems to not put the desired newline at the end of the file.

[xylar]

I went ahead and took care of this in order to get this in. I hope that's okay.

[xylar]

Update: I see you added pre-commit. I've added flake8 andisort here as well:
https://github.com/MPAS-Dev/geometric_features/blob/main/dev-spec.txt#L14-L17

[xylar]

We're purposefully ignoring the flake8 failures here for now. So I will merge without CI passing for now.

[xylar]

Thanks @altheaden!!