Design versioning and release process for localized product documentation

The goal of this issue is to design the versioning and release process for localized GitLab technical documentation. The process / mechanism should integrate the translation workflows with the monthly release process for tech docs.

Scope (to be specified / expanded):

• Design fork-based translation workflow in a way that would allow to handle versioned content
• Implement strategy for mixed-language content that users may experience while translation in ongoing
• Account for the GitLab Pages redirects limit (if this belongs to the context of this issue 🤔 )
• Create process for backporting critical documentation changes to older versions of localized docs content
• Extend CI/CD pipelines to support building and deploying localized versions of docs
• Define SLA for localized releases (unlike simultaneous shipping which is not feasible due to translation naturally lagging in time behind English)
• Document how the monthly docs release process (detailed in releases.md) wil be impacted by (needs to be extended for ?) localized content
• Design the process for handling translation MRs in the fork-based workflow for when a new version branch is cut while translation is ongoing

Relevant original discussions:

• https://gitlab.com/groups/gitlab-com/localization/-/epics/21+
• https://gitlab.com/gitlab-org/technical-writing/team-tasks/-/issues/836+