Bump webpack-dev-server from 2.6.1 to 3.1.11

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.6.1 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@v2.6.1...v3.1.11)

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

package.json

@@ -17,7 +17,7 @@
     "copy-webpack-plugin": "^4.0.1",
     "rimraf": "^2.6.1",
     "webpack": "^3.3.0",
-    "webpack-dev-server": "^2.5.1"
+    "webpack-dev-server": "^3.1.11"
   },
   "dependencies": {
     "axios": "^0.18.1",