npm: bump sass from 1.90.0 to 1.91.0 (#97)

Bumps [sass](https://github.com/sass/dart-sass) from 1.90.0 to 1.91.0.
- [Release notes](https://github.com/sass/dart-sass/releases)
- [Changelog](https://github.com/sass/dart-sass/blob/main/CHANGELOG.md)
- [Commits](sass/dart-sass@1.90.0...1.91.0)

---
updated-dependencies:
- dependency-name: sass
  dependency-version: 1.91.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

package-lock.json

@@ -20,7 +20,7 @@
     "eslint-config-prettier": "^10.1.8",
     "eslint-plugin-prettier": "^5.5.4",
     "prettier": "^3.6.2",
-    "sass": "^1.90.0",
+    "sass": "^1.91.0",
     "vitepress": "^1.6.4"
   }
 }