Bump webpack from 4.30.0 to 4.31.0

Bumps [webpack](https://github.com/webpack/webpack) from 4.30.0 to 4.31.0.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](https://github.com/webpack/webpack/compare/v4.30.0...v4.31.0

)

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