Bump @astrojs/starlight from 0.30.3 to 0.31.0

Bumps [@astrojs/starlight](https://github.com/withastro/starlight/tree/HEAD/packages/starlight) from 0.30.3 to 0.31.0.
- [Release notes](https://github.com/withastro/starlight/releases)
- [Changelog](https://github.com/withastro/starlight/blob/main/packages/starlight/CHANGELOG.md)
- [Commits](https://github.com/withastro/starlight/commits/@astrojs/[email protected]/packages/starlight)

---
updated-dependencies:
- dependency-name: "@astrojs/starlight"
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>