Add Go Report Card badge

Author: markus-wa

README.md

@@ -5,6 +5,7 @@ Is a CS:GO demo parser written in Go based on [Valve's demoinfogo](https://githu
 [![GoDoc](https://godoc.org/github.com/markus-wa/demoinfocs-golang?status.svg)](https://godoc.org/github.com/markus-wa/demoinfocs-golang)
 [![Build Status](https://travis-ci.org/markus-wa/demoinfocs-golang.svg?branch=master)](https://travis-ci.org/markus-wa/demoinfocs-golang)
 [![codecov](https://codecov.io/gh/markus-wa/demoinfocs-golang/branch/master/graph/badge.svg)](https://codecov.io/gh/markus-wa/demoinfocs-golang)
+[![Go Report](https://goreportcard.com/badge/github.com/markus-wa/demoinfocs-golang)](https://goreportcard.com/report/github.com/markus-wa/demoinfocs-golang)
 [![License](https://img.shields.io/badge/license-MIT-blue.svg?style=flat)](LICENSE.md)
 
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