Bump webpack-cli from 3.3.10 to 4.2.0

Bumps [webpack-cli](https://github.com/webpack/webpack-cli) from 3.3.10 to 4.2.0.
- [Release notes](https://github.com/webpack/webpack-cli/releases)
- [Changelog](https://github.com/webpack/webpack-cli/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-cli/compare/v3.3.10...webpack-cli@4.2.0)

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

Author: dependabot-preview[bot]