### Docs update.

  - adding 'what is Dexter' one-liner
  - adding config examples

Self-Review Checklist:

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

✅ Elixir LS update -
[PR](https://github.com/zed-extensions/elixir/pull/115) merged

Release Notes:
- N/A

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Co-authored-by: AltCode <altcode@vivaldi.net>