Lima docs should be generated from the release, not from `master`

We currently have only a single docs site that is generated from the docs tree from `master`.

This makes it difficult to document changes or new features because the text then has to document both the current state and the new state in a single document.

It also means that the docs need to be manually updated again after each release.

It would make more sense to publish the docs from the last tagged (non-alpha/beta/rc) release.

The current state of the docs from `master` could be published on a different URL, or just using GitHub pages, and the link to these docs should be somewhat hidden in the developer docs, so users don't look there for the current docs.

Ideally the doc generator would create a banner on the dev docs that displays a warning about it, and contains a link to the released docs.