add idempotency on documentation

README.md

@@ -29,18 +29,23 @@ require 'mercadopago'
 
 sdk = Mercadopago::SDK.new('YOUR_ACCESS_TOKEN')
 
-payment_data = {
-  transaction_amount: 100,
-  token: 'CARD_TOKEN',
-  description: 'Payment description',
-  payment_method_id: 'visa',
-  installments: 1,
-  payer: {
-    email: '[email protected]'
+custom_headers = {
+ 'x-idempotency-key': '<SOME_UNIQUE_VALUE>'
+}
+
+custom_request_options = Mercadopago::RequestOptions.new(custom_headers: custom_headers)
+
+payment_request = {
+  transaction_amount: 100, 
+  token: 'CARD_TOKEN', 
+  installments: 1, 
+  payer: { 
+    type: 'customer', 
+    id: '123456789-jxOV430go9fx2e'
   }
 }
-result = sdk.payment.create(payment_data)
-payment = result[:response]
+payment_response = sdk.payment.create(payment_request, custom_request_options)
+payment = payment_response[:response]
 
 puts payment
 ```