chore(deps-dev): bump webpack-dev-middleware from 4.3.0 to 5.0.0

Bumps [webpack-dev-middleware](https://github.com/webpack/webpack-dev-middleware) from 4.3.0 to 5.0.0.
- [Release notes](https://github.com/webpack/webpack-dev-middleware/releases)
- [Changelog](https://github.com/webpack/webpack-dev-middleware/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-dev-middleware/compare/v4.3.0...v5.0.0)

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

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

packages/fxa-content-server/package.json

@@ -173,7 +173,7 @@
     "ts-node": "^10.0.0",
     "upng-js": "2.1.0",
     "url-loader": "4.1.1",
-    "webpack-dev-middleware": "^4.3.0",
+    "webpack-dev-middleware": "^5.0.0",
     "xmlhttprequest": "git://github.com/mozilla-fxa/node-XMLHttpRequest.git#onerror",
     "yargs": "^17.0.1"
   },