Previously the rule documentation referenced configuration options
via full https:// URLs, which was bad for several reasons:
* changing the website would mean you'd have to change all URLs
* the links didn't work when building mkdocs locally
* the URLs showed up in the `ruff rule` output
* broken references weren't detected by our CI
This commit solves all of these problems by post-processing the
Markdown, recognizing sections such as:
## Options
* `flake8-tidy-imports.ban-relative-imports`
`cargo dev generate-all` will automatically linkify such references
and panic if the referenced option doesn't exist.
Note that the option can also be linked in the other Markdown sections
via e.g. [`flake8-tidy-imports.ban-relative-imports`] since
the post-processing code generates a CommonMark link definition.
Resolves#2766.
