Plugin versioned documentation

[mashhurs]

Description

VPR is built with plugin main branch. However, elastic_integration plugin releases from other branches and the docs of those releases are not reflecting in the VPR: https://www.elastic.co/docs/reference/logstash/versioned-plugins/filter-elastic_integration-index
If we forget forward porting the release notes to the changelog, the released version will not be visible.

This issue's goal is to discuss such caveats and think if we can find a way improve doc visibility of released version from branch.