Bump astro from 5.18.1 to 6.1.5

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.18.1 to 6.1.5.
- [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@6.1.5/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 6.1.5
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

docs/package.json

@@ -12,7 +12,7 @@
   "dependencies": {
     "@astrojs/check": "^0.9.6",
     "@astrojs/starlight": "^0.37.7",
-    "astro": "^5.18.1",
+    "astro": "^6.1.5",
     "sharp": "^0.34.5",
     "typescript": "^5.9.3",
     "zod": "^3.25.76"