Bump webpack-dev-server from 2.11.2 to 3.1.11

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.11.2 to 3.1.11.
- [Release notes](https://github.com/webpack/webpack-dev-server/releases)
- [Changelog](https://github.com/webpack/webpack-dev-server/blob/master/CHANGELOG.md)
- [Commits](webpack/webpack-dev-server@v2.11.2...v3.1.11)

---
updated-dependencies:
- dependency-name: webpack-dev-server
  dependency-type: direct:development
...

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

Author: dependabot[bot]