build(deps): bump nth-check and unist-util-select in /website

Bumps [nth-check](https://github.com/fb55/nth-check) to 2.1.1 and updates ancestor dependency [unist-util-select](https://github.com/syntax-tree/unist-util-select). These dependencies need to be updated together.


Updates `nth-check` from 1.0.2 to 2.1.1
- [Release notes](https://github.com/fb55/nth-check/releases)
- [Commits](fb55/nth-check@v1.0.2...v2.1.1)

Updates `unist-util-select` from 2.0.2 to 4.0.1
- [Release notes](https://github.com/syntax-tree/unist-util-select/releases)
- [Commits](syntax-tree/unist-util-select@2.0.2...4.0.1)

---
updated-dependencies:
- dependency-name: nth-check
  dependency-type: indirect
- dependency-name: unist-util-select
  dependency-type: direct:production
...

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