Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 4.1.5 to 4.2.1.
- [Release notes](https://github.com/survivejs/webpack-merge/releases)
- [Changelog](https://github.com/survivejs/webpack-merge/blob/master/CHANGELOG.md)
- [Commits](https://github.com/survivejs/webpack-merge/compare/v4.1.5...v4.2.1

)

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