docs(vscode): include information regarding random test ordering (#830)

Author: alestiago

extensions/vscode/CONTRIBUTING.md

@@ -75,6 +75,8 @@ npm run lint
 npm test
 ```
 
+💡 **Note**: As contributors we should avoid cross-test dependencies. We rely on Mocha as our testing framework, unfortunately, it doesn't yet support [randomized test ordering](https://github.com/mochajs/mocha/issues/902).
+
 5. Create the Pull Request with a meaningful description, linking to the original issue where possible.
 
 6. Verify that all [status checks](https://github.com/VeryGoodOpenSource/dart_frog/actions/) are passing for your Pull Request once they have been approved to run by a maintainer.