Bump webpack-dev-server from 2.11.5 to 3.1.11

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.11.5 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](https://github.com/webpack/webpack-dev-server/commits/v3.1.11)

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

Author: dependabot[bot]

package.json

@@ -69,7 +69,7 @@
     "style-loader": "^0.19.1",
     "webpack": "^3.12.0",
     "webpack-concat-plugin": "^2.4.2",
-    "webpack-dev-server": "^2.11.5",
+    "webpack-dev-server": "^3.1.11",
     "webpack-md5-hash": "0.0.6",
     "write-file-webpack-plugin": "^4.4.1"
   },