Document `auto_update_extensions` setting (#58954)

Originally added in https://github.com/zed-industries/zed/pull/46130 but
accidentally dropped in
https://github.com/zed-industries/zed/pull/45276. Bring it back, as
we’ve actually had users ask about this previously and
[recently](https://zed-industries.slack.com/archives/C0AJ37231HS/p1779466189363979),
as well.

Self-Review Checklist:

- [ ] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [ ] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [ ] Tests cover the new/changed behavior
- [ ] Performance impact has been considered and is acceptable


Release Notes:

- N/A

---------

Co-authored-by: zed-zippy[bot] <234243425+zed-zippy[bot]@users.noreply.github.com>
0387238261Kunall Banerjee committed on 6/10/2026, 3:50:24 PM· committed by GitHubparent7220d88
1 file changedLine totals unavailable