build(deps-dev): bump css-loader from 5.1.1 to 5.1.3 in /frontend

Bumps [css-loader](https://github.com/webpack-contrib/css-loader) from 5.1.1 to 5.1.3.
- [Release notes](https://github.com/webpack-contrib/css-loader/releases)
- [Changelog](https://github.com/webpack-contrib/css-loader/blob/master/CHANGELOG.md)
- [Commits](webpack-contrib/css-loader@v5.1.1...v5.1.3)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

frontend/package-lock.json

@@ -26,7 +26,7 @@
     "babel-plugin-prismjs": "^2.0.0",
     "babel-polyfill": "^6.26.0",
     "clean-webpack-plugin": "^3.0.0",
-    "css-loader": "^5.1.1",
+    "css-loader": "^5.1.3",
     "css-minimizer-webpack-plugin": "^1.2.0",
     "eslint": "^7.21.0",
     "eslint-config-prettier": "^6.2.0",