Add numpydoc section name checker

[DanielNoord]

Follow up to https://github.com/DanielNoord/pydocstringformatter/pull/248.

I think the idea of that PR should still be pursued and I don't want to lose the branch. I haven't figured out a good way to do it though. How can we display that pydocstringformatter can't format the code in a nice way..

[github-actions[bot]]

According to the primer, this change has no effect on the checked open source code. 🤖🎉