publish.md: add bits about the new auto-release feature
Created by: mlutfy
3 changes:
- minor: changed a "CiviCRM-native" for just "CiviCRM", because I'm not a fan of the term, and it's kind of repeated in the next paragraph.
- for requesting permission, I added that they can ask on Mattermost. I think it provides more transparency than writing to info@civicrm.org (and I don't get a copy of those emails).
- added a paragraph about Gitlab and faster releases.