Description of the change

Routine PR bringing changes in main into develop after the 0.8.2 release.

Progress of the PR

• Docstrings for all functions
• Unit tests with pytest for all lines
• Clean code style by running black via pre-commit

Minimal example of the bug fix or new feature

>>> import kikuchipy as kp
>>> s = kp.data.nickel_ebsd_small()
>>> s
<EBSD, title: patterns Scan 1, dimensions: (3, 3|60, 60)>
>>> # Your new feature...

For reviewers

• The PR title is short, concise, and will make sense 1 year later.
• New functions are imported in corresponding __init__.py.
• New features, API changes, and deprecations are mentioned in the unreleased
  section in CHANGELOG.rst.
• New contributors are added to release.py, .zenodo.json and
  .all-contributorsrc with the table regenerated.