message: docs: Mention sandbox implications
diff: @@ -45,6 +45,8 @@ const auth = {
  apiKey: '',
  apiSecret: '',
  passphrase: '',
  + // The Sandbox is for testing only and offers a subset of the products/assets:
  + // https://docs.pro.coinbase.com/#sandbox
  useSandbox: true,
  };
  