chore(deps-dev): bump webpack-cli from 3.3.12 to 4.6.0 in /client

Bumps [webpack-cli](https://github.com/webpack/webpack-cli) from 3.3.12 to 4.6.0.
- [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/v3.3.12...webpack-cli@4.6.0)

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