Bump webpack from 4.26.1 to 4.31.0 in /webpack

Bumps [webpack](https://github.com/webpack/webpack) from 4.26.1 to 4.31.0.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](webpack/webpack@v4.26.1...v4.31.0)

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

Author: dependabot-support