v0.58.0

Comments can be switched for a whole handbook, not only page by page: leave it to each page, or open or close comments for every page of that handbook at once, under Handbook, Handbooks. Closing hides the form; comments already written stay and are not deleted.

Links to another website are no longer broken by the import. A link whose address ends in .md was treated as a link inside the import even when it pointed at github.com, so it was stripped to plain text and reported as a dead link. A fresh installation of the shipped handbook reported six of them.

Documentation: README and CONTRIBUTING now describe what CI actually runs, docs/ has an index and a reading order, the release process is written down in docs/releasing.md, and .wp-env.json gives a working WordPress in two commands.

Nothing needs doing on update; the new comment setting arrives switched off.