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 1.2.0 to 2.0.0.
- [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/css-minimizer-webpack-plugin@v1.2.0...v2.0.0)

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

Author: dependabot[bot]