Should be staged with sr#1128267, sr#1128266

- Update to version 2.0.0:
- This release primarily updates core myst-parser dependencies, with
some minor changes to parsing behaviour:
- UPGRADE: markdown-it-py to v3 (#773)
- This is mainly a non-breaking change, fixing some edge cases in parsing
- See: https://github.com/executablebooks/markdown-it-py/releases/tag/v3.0.0
- and https://github.com/executablebooks/mdit-py-plugins/releases/tag/v0.4.0
- UPGRADE: linkify-it-py to v2 (#675)
- Also fixes some edge cases in parsing
- See: https://github.com/tsutsu3/linkify-it-py/blob/main/CHANGELOG.md
- UPGRADE: Add support for docutils v0.20 (#775)
- No significant changes, see https://docutils.sourceforge.io/RELEASE-NOTES.html#release-0-20-2023-05-04
- UPGRADE: Add support for sphinx v7, and remove v5 support (#776)
- No significant changes, see https://www.sphinx-doc.org/en/master/changes.html
- UPGRADE: Remove Python 3.7 support and add testing for Python
3.11 (#772)
- Improve default slug generation for heading anchors, thanks to
@Cimbali (#777)
- This change makes the slug generation closer to GitHub, in
that, starting/ending whitespace will not be stripped.
- For example, # ` a` b `c ` will now correctly create the slug
-a-b-c- and not a-b-c
- IMPROVE: Substitution extension (#777)
- Allow any value type (including dict, list, datetime) and emit
a myst.substitution warning for errors in resolving the
substitution content.
- Introduce a gate/check GHA job, thanks to @webknjaz (#635)
- v1.0.0:
- This changes absolutely nothing in the code, or about the
maintenance/release policy of this project. But it does feel