Add README for example

Author: maria-robobug

_code-samples/issue-credentials/js/README.md

@@ -0,0 +1,12 @@
+# Credential Issuing Service - Python sample code
+
+This code implements an HTTP API that issues credentials on the XRPL on request.
+
+Quick install & usage:
+
+```sh
+npm install
+node issuer_service.js
+```
+
+For more detail, see the full tutorial for [How to build a service that issues credentials on the XRP Ledger](https://xrpl.org/docs/tutorials/javascript/build-apps/credential-issuing-service).