Bump webpack-dev-server in /src/CmsBundle/Resources/xms

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 1.16.5 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@v1.16.5...v3.1.11)

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

Author: dependabot[bot]

src/CmsBundle/Resources/xms/package.json

@@ -75,7 +75,7 @@
     "tether": "^1.3.4",
     "url-loader": "^0.5.7",
     "webpack": "^1.13.2",
-    "webpack-dev-server": "^1.14.1"
+    "webpack-dev-server": "^3.1.11"
   },
   "devDependencies": {
     "babel-core": "^6.13.2",