build(deps): bump astro from 4.16.4 to 5.15.9

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 4.16.4 to 5.15.9.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/astro/CHANGELOG-v4.md)
- [Commits](https://github.com/withastro/astro/commits/astro@5.15.9/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 5.15.9
  dependency-type: direct:production
...

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

package.json

@@ -17,7 +17,7 @@
   "dependencies": {
     "@astrojs/rss": "^2.4.1",
     "@resvg/resvg-js": "^2.4.1",
-    "astro": "^4.16.4",
+    "astro": "^5.15.9",
     "fuse.js": "^6.6.2",
     "github-slugger": "^2.0.0",
     "remark-collapse": "^0.1.2",