chore(deps-dev): bump cssnano from 5.1.15 to 6.0.0 in /frontend (#1359)

Bumps [cssnano](https://github.com/cssnano/cssnano) from 5.1.15 to 6.0.0.
- [Release notes](https://github.com/cssnano/cssnano/releases)
- [Commits](https://github.com/cssnano/cssnano/compare/cssnano@5.1.15...cssnano@6.0.0)

---
updated-dependencies:
- dependency-name: cssnano
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

frontend/package.json

@@ -30,7 +30,7 @@
 		"@typescript-eslint/parser": "^5.48.0",
 		"@zerodevx/svelte-toast": "^0.8.1",
 		"autoprefixer": "^10.4.13",
-		"cssnano": "^5.1.14",
+		"cssnano": "^6.0.0",
 		"d3-dag": "^0.11.5",
 		"eslint": "^8.28.0",
 		"eslint-config-prettier": "^8.6.0",