chore: update message

README.md

@@ -44,7 +44,7 @@ For a full list of available resources, visit the [GoCardless API reference](htt
 ```js
 const uuidv4 = require('uuid/v4');
 
-// Create a new payment.
+// Create a new payment with an idempotency key
 const payment = await client.payments.create(
   {
     amount: 100,