build(deps): bump astro from 5.16.0 to 5.18.1

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.16.0 to 5.18.1.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/astro@5.18.1/packages/astro/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/astro@5.18.1/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 5.18.1
  dependency-type: direct:production
...

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

package.json

@@ -24,7 +24,7 @@
     "@niivue/dicom-loader": "^1.0.0",
     "@niivue/itkwasm-loader": "^1.0.2",
     "@niivue/niivue": "^0.64.0",
-    "astro": "^5.15.9",
+    "astro": "^5.18.1",
     "client-zip": "^2.5.0",
     "fuse.js": "^7.1.0",
     "highlight.js": "^11.11.1",