Improve qualitative orientation analysis in user guide

[hakonanes]

Description of the change

• Improve the qualitative orientation analysis in the pattern matching user guide with newest inverse pole figure (IPF) functionality in orix 0.8.
• Store cell output in the pattern matching notebook so it doesn't have to be built on the Readthedocs (RTD) server. This is necessary because without storing cell output, the RTD server takes 800 s out of 900 available s to build our docs, which is too close to the limit. All notebooks are tested every Monday morning via a GitHub Action, so it isn't so dangerous that this notebook isn't tested on every (PR) commit.
• Restrict lowest version of orix to 0.8.
• Update year in license to 2019-2022
• Remove unnecessary encoding notice in the first line of Python files

See the docs built from this PR for the user guide changes.

Progress of the PR

• Docstrings for all functions
• Unit tests with pytest for all lines
• Clean code style by running black via pre-commit
• Complete other minor updates of user guide notebooks
• Make a convenience function in kikuchipy.draw to create an RGB navigator
• Prepare changelog for release
• Bump release version to 0.5.6

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 .all-contributorsrc and the table is regenerated.

[hakonanes]

I'll release 0.5.6 tomorrow.