Bump mini-css-extract-plugin from 2.7.6 to 2.8.1 in /frontend (#1084)

Bumps [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) from 2.7.6 to 2.8.1.
- [Release notes](https://github.com/webpack-contrib/mini-css-extract-plugin/releases)
- [Changelog](https://github.com/webpack-contrib/mini-css-extract-plugin/blob/master/CHANGELOG.md)
- [Commits](webpack-contrib/mini-css-extract-plugin@v2.7.6...v2.8.1)

---
updated-dependencies:
- dependency-name: mini-css-extract-plugin
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

frontend/package.json

@@ -26,7 +26,7 @@
     "eslint-plugin-react-hooks": "^4.6.0",
     "html-webpack-harddisk-plugin": "^2.0.0",
     "html-webpack-plugin": "^5.6.0",
-    "mini-css-extract-plugin": "^2.7.2",
+    "mini-css-extract-plugin": "^2.8.1",
     "mocha": "^10.1.0",
     "sinon-chai": "^3.7.0",
     "stylus": "^0.62.0",