[ADD] https://godoc.org/github.com/Frontware/promptpay

Author: efairon

README.md

@@ -18,6 +18,12 @@ Golang API to generate QRCode
 
 ## Documentation
 
+### API
+
+https://godoc.org/github.com/Frontware/promptpay
+
+### Specifications
+
 EMV QR Code specification: https://www.emvco.com/wp-content/plugins/pmpro-customizations/oy-getfile.php?u=/wp-content/uploads/documents/EMVCo-Consumer-Presented-QR-Specification-v1.pdf
 
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