Relax space group requirement when creating phase from CIF

[hakonanes]

Description of the change

This PR addresses #505 by using a try/except to potentially skip the space group if diffpy.structure could not read it.

@OverEthanol, can you test this branch and see if you can read your file?

This PR also replaces Union[X, Y] with X | Y in type hints in the crystal_map.phase_list module.

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

>>> from orix.crystal_map import Phase
>>> Phase.from_cif("ZIF-L_1509273.cif")
<name: ZIF-L_1509273. space group: Cmca. point group: mmm. proper point group: 222. color: tab:blue>

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.
• Contributor(s) are listed correctly in __credits__ in orix/__init__.py and in
  .zenodo.json.

[pc494]

Perfect, merging.