Bump postcss-loader from 7.3.3 to 8.1.1

Bumps [postcss-loader](https://github.com/webpack-contrib/postcss-loader) from 7.3.3 to 8.1.1.
- [Release notes](https://github.com/webpack-contrib/postcss-loader/releases)
- [Changelog](https://github.com/webpack-contrib/postcss-loader/blob/master/CHANGELOG.md)
- [Commits](webpack-contrib/postcss-loader@v7.3.3...v8.1.1)

---
updated-dependencies:
- dependency-name: postcss-loader
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

package-lock.json

@@ -26,7 +26,7 @@
         "highlight.js": "^11.9.0",
         "leaflet": "^1.9.4",
         "postcss": "^8.4.31",
-        "postcss-loader": "^7.3.3",
+        "postcss-loader": "^8.1.1",
         "prop-types": "^15.8.1",
         "react": "^18.2.0",
         "react-dom": "^18.2.0",