Bump astro from 5.7.13 to 5.12.8 in /docs (#1147)

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.7.13 to 5.12.8.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/astro/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/astro@5.12.8/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 5.12.8
  dependency-type: direct:production
...

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docs/package.json

@@ -12,7 +12,7 @@
   "dependencies": {
     "@astrojs/check": "^0.9.3",
     "@astrojs/starlight": "^0.34.3",
-    "astro": "^5.7.13",
+    "astro": "^5.12.8",
     "sharp": "^0.32.5",
     "typescript": "^5.6.2"
   }