🐈 Add built-in styling for Sphinx-annotated ASTs

[agoose77]

In #431 I explored adding pass-through rendering support for Sphinx AST nodes (generated from a separate extension for Sphinx). This PR instead looks for annotations on a canonical MyST AST to make the styling required to improve Sphinx rendering. Currently this is only focused on autodoc nodes.

There are some limitations in our AST right now that make this a bit fiddly, namely that many node types don't support custom classes. Consequently, some of the selectors are more like heuristics, but they are all gated on a parent class starting with sphinx-.

[changeset-bot]

🦋 Changeset detected

Latest commit: caa99a4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 12 packages

Name	Type
@myst-theme/styles	Patch
@myst-theme/providers	Patch
@myst-theme/frontmatter	Patch
@myst-theme/diagrams	Patch
@myst-theme/jupyter	Patch
@myst-theme/site	Patch
@myst-theme/common	Patch
@myst-theme/icons	Patch
@myst-theme/book	Patch
@myst-theme/article	Patch
myst-to-react	Patch
myst-demo	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[agoose77]

This styling isn't perfect, but it's simple enough to start with.