build(deps-dev): update css-loader requirement in /web

Updates the requirements on [css-loader](https://github.com/webpack-contrib/css-loader) to permit the latest version.
- [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/v6.3.0...v6.5.0)

---
updated-dependencies:
- dependency-name: css-loader
  dependency-type: direct:development
...

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

web/packages/demo/package.json

@@ -12,7 +12,7 @@
         "ruffle-core": "^0.1.0"
     },
     "devDependencies": {
-        "css-loader": "^6.3.0",
+        "css-loader": "^6.5.0",
         "style-loader": "^3.3.0",
         "webpack-cli": "^4.8.0"
     }