add gorepocard badge

Author: mattn

README.md

@@ -1,9 +1,10 @@
 go-sqlite3
 ==========
 
+[![GoDoc Reference](https://godoc.org/github.com/mattn/go-sqlite3?status.svg)](http://godoc.org/github.com/mattn/go-sqlite3)
 [![Build Status](https://travis-ci.org/mattn/go-sqlite3.svg?branch=master)](https://travis-ci.org/mattn/go-sqlite3)
 [![Coverage Status](https://coveralls.io/repos/mattn/go-sqlite3/badge.svg?branch=master)](https://coveralls.io/r/mattn/go-sqlite3?branch=master)
-[![GoDoc](https://godoc.org/github.com/mattn/go-sqlite3?status.svg)](http://godoc.org/github.com/mattn/go-sqlite3)
+[![Go Report Card](https://goreportcard.com/badge/github.com/mattn/go-sqlite3)](https://goreportcard.com/report/github.com/mattn/go-sqlite3)
 
 Description
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