JSX and TSX only treated the dot as a tag-name character during
linked-editing, so renaming a tag to a custom element name such as
`custom-el` stopped mirroring the closing tag at the dash.

A follow-up to https://github.com/zed-industries/zed/pull/43179, really.

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)
- [x] Tests cover the new/changed behavior
- [ ] Performance impact has been considered and is acceptable

Closes #58553.

Release Notes:

- Added support for linked-editing of custom elements in JSX/TSX

---------

Co-authored-by: MrSubidubi <finn@zed.dev>