Upgrade: Bump webpack-merge from 5.8.0 to 5.9.0

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 5.8.0 to 5.9.0.
- [Changelog](https://github.com/survivejs/webpack-merge/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/survivejs/webpack-merge/commits)

---
updated-dependencies:
- dependency-name: webpack-merge
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>