2.13.0a2 release notes

[joshmoore]

Add recent notes e.g. for #1123, #1085, #934 which could use some testing.

(@madsbk I note from the TODO list below that a next step would be an update to the tutorial with meta_array)

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/tutorial.rst
• Changes documented in docs/release.rst
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[joshmoore]

CSS fun now corrected. Moving forward with 2.13.0a2 via the GH-only release style from #1119