Hello, this is my first time contributing here! The issue creation
button noted that "feature request"-esque items should go to
discussions, so with this PR, I'm closing that discussion and not an
issue. I hope that's ok :)

---

Closes https://github.com/zed-industries/zed/discussions/43769

Preview:

<img width="500" alt="image"
src="https://github.com/user-attachments/assets/00b8d475-d452-42e9-934b-ee5dbe48586e"
/><p/>

Release Notes:

- Added JavaScript highlighting via YAML `injections.scm` for script
blocks of `actions/github-script`