Bump astro from 4.16.3 to 4.16.18 in /docs (#929)

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 4.16.3 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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docs/package.json

@@ -12,7 +12,7 @@
   "dependencies": {
     "@astrojs/check": "^0.9.3",
     "@astrojs/starlight": "^0.27.1",
-    "astro": "^4.16.3",
+    "astro": "^4.16.18",
     "sharp": "^0.32.5",
     "typescript": "^5.6.2"
   }