[Security] Bump webpack-dev-server from 2.11.3 to 3.1.11

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.11.3 to 3.1.11. **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/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-dev-server/compare/v2.11.3...v3.1.11)

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

package.json

@@ -126,7 +126,7 @@
     "vue-style-loader": "^3.0.1",
     "vue-template-compiler": "^2.4.2",
     "webpack": "^3.5.2",
-    "webpack-dev-server": "^2.7.1",
+    "webpack-dev-server": "^3.1.11",
     "webpack-hot-middleware": "^2.18.2",
     "webpack-merge": "^4.1.0"
   }