build(deps): bump astro from 5.14.6 to 5.15.6

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.14.6 to 5.15.6.
- [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/[email protected]/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 5.15.6
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package.json

@@ -13,7 +13,7 @@
     "@niivue/dicom-loader": "^1.0.0",
     "@niivue/itkwasm-loader": "^1.0.2",
     "@niivue/niivue": "^0.64.0",
-    "astro": "^5.14.5",
+    "astro": "^5.15.6",
     "client-zip": "^2.5.0",
     "fuse.js": "^7.1.0",
     "highlight.js": "^11.11.1",