Fix svelte injections / outline (#8194)

This PR fixes the buffer symbol search to show `js` and `ts` buffer
symbols when using svelte components with `ts`.

Does also seem to improve `ts` capabilities (probably because there has
been a conflict of `js` and `ts` before).

Unfortunately when changing the script tag from no lang attribute to
`ts` one needs to update the file (input anyting) to get correct buffer
symbol search.

Before:

![SCR-20240222-mthf-2](https://github.com/zed-industries/zed/assets/67913738/980cf4bf-15d5-478d-a217-ed8f2b1f197d)

After:

![SCR-20240222-mvjr](https://github.com/zed-industries/zed/assets/67913738/41069e75-77ef-40fe-92d1-c19912b34770)

Release Notes:

- Fixed svelte outlines for `TS`.