See:
https://github.com/zed-extensions/ocaml/blob/626cf8e76103fb2d8ea62fc06095df669aca4441/languages/mlx/config.toml#L3

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [x] 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

Release Notes:

- Associate .mlx extensions with OCaml