Bump webpack-merge from 5.8.0 to 5.9.0

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 5.8.0 to 5.9.0.
- [Changelog](https://github.com/survivejs/webpack-merge/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/survivejs/webpack-merge/commits)

---
updated-dependencies:
- dependency-name: webpack-merge
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

package.json

@@ -66,7 +66,7 @@
     "webpack-cli": "^5.1.1",
     "webpack-dev-server": "^4.15.0",
     "webpack-manifest-plugin": "^5.0.0",
-    "webpack-merge": "^5.7.3"
+    "webpack-merge": "^5.9.0"
   },
   "dependencies": {
     "annotator": "wallabag/annotator#master",