[Docs Site] Bump rehype-mermaid from 2.1.0 to 3.0.0

Bumps [rehype-mermaid](https://github.com/remcohaszing/rehype-mermaid) from 2.1.0 to 3.0.0.
- [Release notes](https://github.com/remcohaszing/rehype-mermaid/releases)
- [Commits](remcohaszing/rehype-mermaid@v2.1.0...v3.0.0)

---
updated-dependencies:
- dependency-name: rehype-mermaid
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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