Bump webpack-dev-server from 2.9.5 to 3.1.11 (#14)

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 2.9.5 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@v2.9.5...v3.1.11)

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

Author: dependabot[bot]

package.json

@@ -12,7 +12,7 @@
   "devDependencies": {
     "graphql-tag": "^2.9.2",
     "webpack": "^3.8.1",
-    "webpack-dev-server": "^2.9.5"
+    "webpack-dev-server": "^3.1.11"
   },
   "dependencies": {
     "loader-utils": "^1.1.0",