Update README.md

Author: aafeher

README.md

@@ -1,6 +1,7 @@
 # go-microdata-extract
 
 [![codecov](https://codecov.io/gh/aafeher/go-microdata-extract/graph/badge.svg?token=BD1QYCZESR)](https://codecov.io/gh/aafeher/go-microdata-extract)
+[![Go Report Card](https://goreportcard.com/badge/github.com/aafeher/go-microdata-extract)](https://goreportcard.com/report/github.com/aafeher/go-microdata-extract)
 
 A Go package for extracting structured data from HTML.