Bump clean-css-cli from 5.5.2 to 5.6.0

Bumps [clean-css-cli](https://github.com/clean-css/clean-css-cli) from 5.5.2 to 5.6.0.
- [Release notes](https://github.com/clean-css/clean-css-cli/releases)
- [Changelog](https://github.com/clean-css/clean-css-cli/blob/master/History.md)
- [Commits](https://github.com/clean-css/clean-css-cli/compare/v5.5.2...v5.6.0)

---
updated-dependencies:
- dependency-name: clean-css-cli
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

package.json

@@ -64,7 +64,7 @@
     "@types/topojson-specification": "^1.0.1",
     "babel-loader": "^8.2.2",
     "chaikin-smooth": "^1.0.4",
-    "clean-css-cli": "5.5.2",
+    "clean-css-cli": "5.6.0",
     "copy-webpack-plugin": "^10.0.0",
     "es-main": "^1.0.2",
     "eslint": "^8.0.1",