Bump webpack-dev-server from 2.7.1 to 3.1.11

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.7.1 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@v2.7.1...v3.1.11)

Author: dependabot[bot]

package.json

@@ -54,7 +54,7 @@
     "typescript": "3",
     "url-loader": "0.5.9",
     "webpack": "3.5.1",
-    "webpack-dev-server": "2.7.1",
+    "webpack-dev-server": "3.1.11",
     "webpack-manifest-plugin": "1.2.1",
     "source-map-loader": "^0.2.1",
     "style-loader": "0.18.2",