add goreport badge (ratify-project#337)

Signed-off-by: David Tesar <[email protected]>

README.md

@@ -5,6 +5,7 @@ Is a policy engine as a binary executable and on Kubernetes which enables verifi
 **WARNING:** This is not considered production-grade code
 by its developers, nor is it "supported" software.
 
+[![Go Report Card](https://goreportcard.com/badge/github.com/deislabs/ratify)](https://goreportcard.com/report/github.com/deislabs/ratify)
 [![build-pr](https://github.com/deislabs/ratify/actions/workflows/build-pr.yml/badge.svg)](https://github.com/deislabs/ratify/actions/workflows/build-pr.yml)
 [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/deislabs/ratify/badge)](https://api.securityscorecards.dev/projects/github.com/deislabs/ratify)