build(deps-dev): bump css-minimizer-webpack-plugin in /frontend

Bumps [css-minimizer-webpack-plugin](https://github.com/webpack-contrib/css-minimizer-webpack-plugin) from 1.1.5 to 1.2.0.
- [Release notes](https://github.com/webpack-contrib/css-minimizer-webpack-plugin/releases)
- [Changelog](https://github.com/webpack-contrib/css-minimizer-webpack-plugin/blob/master/CHANGELOG.md)
- [Commits](webpack-contrib/css-minimizer-webpack-plugin@v1.1.5...v1.2.0)

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

Author: dependabot[bot]

frontend/package-lock.json

@@ -27,7 +27,7 @@
     "babel-polyfill": "^6.26.0",
     "clean-webpack-plugin": "^3.0.0",
     "css-loader": "^5.0.0",
-    "css-minimizer-webpack-plugin": "^1.1.5",
+    "css-minimizer-webpack-plugin": "^1.2.0",
     "eslint": "^7.18.0",
     "eslint-config-prettier": "^6.2.0",
     "eslint-config-standard": "^16.0.1",