build(deps-dev): bump webpack-dev-server from 1.14.0 to 3.1.11

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 1.14.0 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@v1.14.0...v3.1.11)

---
updated-dependencies:
- dependency-name: webpack-dev-server
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -51,7 +51,7 @@
     "susy": "2.2.5",
     "url-loader": "^0.5.7",
     "webpack": "1.12.9",
-    "webpack-dev-server": "1.14.0"
+    "webpack-dev-server": "3.1.11"
   },
   "manifest.webapp": {
     "name": "DHIS2 event reports app",