Bump css-loader from 3.6.0 to 4.3.0 (#6105)

Bumps [css-loader](https://github.com/webpack-contrib/css-loader) from 3.6.0 to 4.3.0.
- [Release notes](https://github.com/webpack-contrib/css-loader/releases)
- [Changelog](https://github.com/webpack-contrib/css-loader/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack-contrib/css-loader/compare/v3.6.0...v4.3.0)

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package.json

@@ -126,7 +126,7 @@
     "commander": "6.0.0",
     "concurrently": "^5.3.0",
     "cspell": "^4.1.0",
-    "css-loader": "^3.4.2",
+    "css-loader": "^4.3.0",
     "dotenv": "^8.2.0",
     "ejs": "^3.1.5",
     "graphql": "^15.3.0",