To use this in your Qwik e-commerce project, you can add the above code snippet to your serverless function file (typically in the functions directory) and modify it to fit your specific needs. For example, you can replace platform.log with your own custom code that uses the environment variables to hook up Square payments.
Once you have added the code to your serverless function file, you should be able to access the environment variables set in Netlify using process.env.<variable_name> within your serverless functions.
I hope that helps! Let me know if you have any further questions or need any additional clarification.