add Go Report Card

Signed-off-by: Victor Vieux <victorvieux@gmail.com>

Author: vieux

README.md

@@ -3,6 +3,7 @@
 This plugin allows you to mount remote folder using sshfs in your container easily.
 
 [![TravisCI](https://travis-ci.org/vieux/docker-volume-sshfs.svg)](https://travis-ci.org/vieux/docker-volume-sshfs)
+[![Go Report Card](https://goreportcard.com/badge/github.com/vieux/docker-volume-sshfs)](https://goreportcard.com/report/github.com/vieux/docker-volume-sshfs)
 
 ## Usage