* Make CHANGELOG urls clickable
- Add link reference definitions for PRs and new contributors in v0.4.0.rc2
- Replace inline urls by shortcut link references
- Add front matter so the page appears in the navigation
- Change the link to the CHANGELOG on the home page
The CHANGELOG contents should look the same in the docs and in the repo (apart from the callouts) with clickable links to PRs and some contributors.
The urls shown in the changes in v0.4.0.rc1 (and previous releases) haven't yet been made clickable – it would be too tedious and error-prone to do it manually.
* Make CHANGELOG urls clickable
- Add a callout
This PR updates the home page and the CHANGELOG to refer to v0.4.0.rc1 as a pre-release or release candidate, rather than a release. See [this comment](https://github.com/just-the-docs/just-the-docs/pull/613#issuecomment-1240442518) for motivation.
It also adds the versioned docs issue (#728) to the roadmap in the CHANGELOG.
As the config for the theme docs now needs to declare callouts, the [callouts docs](https://just-the-docs.github.io/just-the-docs/docs/ui-components/callouts/) can now illustrate the rendered appearance. (These callouts are merely examples: the names and colors should eventually be replaced by a principled collection, taking account of WCAG.)
