Bump webpack-dev-server from 2.11.1 to 3.1.11

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.11.1 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@v2.11.1...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]

package.json

@@ -56,7 +56,7 @@
     "tslint": "5.18.0",
     "typescript": "~2.7",
     "webpack": "2.6.1",
-    "webpack-dev-server": "2.11.1",
+    "webpack-dev-server": "3.1.11",
     "webpack-merge": "^4.1.0"
   },
   "dependencies": {