[Security] Bump webpack-dev-server from 2.11.5 to 3.11.2

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.11.5 to 3.11.2. **This update includes a security fix.**
- [Release notes](https://github.com/webpack/webpack-dev-server/releases)
- [Changelog](https://github.com/webpack/webpack-dev-server/blob/v3.11.2/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-dev-server/commits/v3.11.2)

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

package.json

@@ -44,7 +44,7 @@
     "stylelint-config-standard": "^20.0.0",
     "webpack": "^3.10.0",
     "webpack-dashboard": "^3.3.1",
-    "webpack-dev-server": "^2.11.5"
+    "webpack-dev-server": "^3.11.2"
   },
   "dependencies": {
     "babel-polyfill": "^6.26.0",