Add coverage badge

Author: lucmq

README.md

@@ -1,6 +1,7 @@
 # Go-Shelve
 [![Go Reference](https://pkg.go.dev/badge/github.com/lucmq/go-shelve/shelve.svg)](https://pkg.go.dev/github.com/lucmq/go-shelve/shelve)
 [![Go Report Card](https://goreportcard.com/badge/github.com/lucmq/go-shelve)](https://goreportcard.com/report/github.com/lucmq/go-shelve)
+[![Go Coverage](https://github.com/lucmq/go-shelve/wiki/coverage.svg)](https://raw.githack.com/wiki/USER/REPO/coverage.html)
 [![DeepSource](https://app.deepsource.com/gh/lucmq/go-shelve.svg/?label=active+issues&show_trend=false&token=iZaN7kSfuZGm1KppBKaqMHME)](https://app.deepsource.com/gh/lucmq/go-shelve/)
 
 Go-Shelve is a dependencies-free Go package that provides a persistent, map-like