Bump webpack-dev-server from 2.4.5 to 3.1.11

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.4.5 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](webpack/webpack-dev-server@v2.4.5...v3.1.11)

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

package.json

@@ -16,7 +16,7 @@
     "css-loader": "^0.28.2",
     "style-loader": "^0.18.0",
     "webpack": "^2.5.1",
-    "webpack-dev-server": "^2.4.5"
+    "webpack-dev-server": "^3.1.11"
   },
   "scripts": {
     "build": "./node_modules/.bin/webpack --progress --color --display-error-details",