Bump webpack-merge from 5.1.3 to 5.1.4

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 5.1.3 to 5.1.4.
- [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/v5.1.3...v5.1.4

)

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