Add pretty-format-yaml pre-commit hook.

[euronion]

Change proposed in this Pull Request

Add a pre-commit hook for formatting yaml files.

Motivation and Context

We have a lot of yaml files and no automatic formatting. This fixes it.

How Has This Been Tested?

By running pre-commit run --all-files locally. This should not break anything, formatting only.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I tested my contribution locally and it seems to work fine.
• [n/a] I locally ran pytest inside the repository and no unexpected problems came up.
• [n/a] I have adjusted the docstrings in the code appropriately.
• [n/a] I have documented the effects of my code changes in the documentation doc/.
• [n/a] I have added newly introduced dependencies to environment.yaml file.
• I have added a note to release notes doc/release_notes.rst.
• I have used pre-commit run --all to lint/format/check my contribution