build(deps): bump astro from 4.15.1 to 4.16.18 in /docs (#590)

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 4.15.1 to 4.16.18.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/astro@4.16.18/packages/astro/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/astro@4.16.18/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-type: direct:production
...

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