Update README to latest release
# What does this PR do?

The main README (and its variants) all have multiple links to released models that point to the main doc and not the stable doc. This is because we did the last two releases on branches different from the main one, so the README cleaned by our tools was not set on the main branch.

This PR fixes that and adds instructions in our release guide.
_The documentation is not available anymore as the PR was closed or merged._