Update CONTRIBUTING link to point to GitHub page

Author: alexander-akait

README.md

@@ -2344,7 +2344,7 @@ We welcome all contributions!
 
 If you are new here, please take a moment to review our contributing guidelines before submitting issues or pull requests.
 
-[CONTRIBUTING](./.github/CONTRIBUTING.md)
+[CONTRIBUTING](https://github.com/webpack/css-loader?tab=contributing-ov-file#contributing)
 
 ## License