Maintaining package credits

Whenever we get a new contributor, they should be added to the package credits. Unless they do not want to, of course. We maintain three separate sources for the list of contributors:

• kikuchipy/release.py: Package metadata used by PyPI and other places

• .zenodo.json: Zenodo entry

• All-contributors table in the README

In the package metadata and the Zenodo entry, the initial commiter is listed first, with the others sorted by line contributions.

The All-contributors table in the README is updated locally using their command line interface (see their web page for the docs).