chore: bump github-slugger from 1.3.0 to 1.4.0

Bumps [github-slugger](https://github.com/Flet/github-slugger) from 1.3.0 to 1.4.0.
- [Release notes](https://github.com/Flet/github-slugger/releases)
- [Changelog](https://github.com/Flet/github-slugger/blob/master/CHANGELOG.md)
- [Commits](Flet/github-slugger@v1.3.0...v1.4.0)

---
updated-dependencies:
- dependency-name: github-slugger
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>