Bump webpack-dev-server from 3.10.3 to 4.8.0 in /example

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 3.10.3 to 4.8.0.
- [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@v3.10.3...v4.8.0)

---
updated-dependencies:
- dependency-name: webpack-dev-server
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

example/package.json

@@ -45,7 +45,7 @@
     "url-loader": "^3.0.0",
     "webpack": "^4.42.0",
     "webpack-cli": "^3.3.11",
-    "webpack-dev-server": "^3.10.3"
+    "webpack-dev-server": "^4.8.0"
   },
   "standard": {
     "globals": [