Docs: Show stage and group frontmatter
In each doc, we have this frontmatter:
---
stage: Enablement
group: Geo
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
---
But it is not shown in the rendered site, e.g. https://docs.gitlab.com/ee/administration/maintenance_mode/
For transparency, propose we show this information.