Bump @csstools/postcss-cascade-layers from 5.0.2 to 6.0.0

Bumps [@csstools/postcss-cascade-layers](https://github.com/csstools/postcss-plugins/tree/HEAD/plugins/postcss-cascade-layers) from 5.0.2 to 6.0.0.
- [Changelog](https://github.com/csstools/postcss-plugins/blob/main/plugins/postcss-cascade-layers/CHANGELOG.md)
- [Commits](https://github.com/csstools/postcss-plugins/commits/HEAD/plugins/postcss-cascade-layers)

---
updated-dependencies:
- dependency-name: "@csstools/postcss-cascade-layers"
  dependency-version: 6.0.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

package-lock.json

@@ -46,7 +46,7 @@
   },
   "devDependencies": {
     "@biomejs/biome": "2.3.11",
-    "@csstools/postcss-cascade-layers": "5.0.2",
+    "@csstools/postcss-cascade-layers": "6.0.0",
     "@rsbuild/core": "1.7.2",
     "@rsbuild/plugin-react": "1.4.2",
     "@rsbuild/plugin-svgr": "1.2.4",