Add scorecard badge

README.md

@@ -2,6 +2,7 @@
 [![CircleCI](https://circleci.com/gh/rsksmart/rskj/tree/master.svg?style=svg)](https://circleci.com/gh/rsksmart/rskj/tree/master)
 [![Quality Gate Status](https://sonarcloud.io/api/project_badges/measure?project=rskj&metric=alert_status)](https://sonarcloud.io/dashboard?id=rskj)
 [![CodeQL](https://github.com/rsksmart/rskj/workflows/CodeQL/badge.svg)](https://github.com/rsksmart/rskj/actions?query=workflow%3ACodeQL)
+[![OpenSSF Scorecard](https://api.scorecard.dev/projects/github.com/rsksmart/rskj/badge)](https://scorecard.dev/viewer/?uri=github.com/rsksmart/rskj)
 
 # About
 RskJ is a Java implementation of the Rootstock node. For more information about Rootstock, visit [rootstock.io](https://rootstock.io/). The [Rootstock white paper](https://rootstock.io/rsk-white-paper-updated.pdf) provides a complete conceptual overview of the platform.