Bump webpack-cli from 3.1.2 to 3.3.2 in /slides

Bumps [webpack-cli](https://github.com/webpack/webpack-cli) from 3.1.2 to 3.3.2.
- [Release notes](https://github.com/webpack/webpack-cli/releases)
- [Changelog](https://github.com/webpack/webpack-cli/blob/master/CHANGELOG.md)
- [Commits](webpack/webpack-cli@v3.1.2...v3.3.2)

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Author: dependabot-support