Bump webpack-dev-server from 4.9.0 to 4.9.1 (#600)

Bump webpack-dev-server from 4.9.0 to 4.9.1 (#600)

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 4.9.0 to 4.9.1.
- [Release notes](https://github.com/webpack/webpack-dev-server/releases)
- [Changelog](https://github.com/webpack/webpack-dev-server/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-dev-server/compare/v4.9.0...v4.9.1)

---
updated-dependencies:
- dependency-name: webpack-dev-server
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>