chore(README): update badges

README.md

@@ -1,5 +1,10 @@
 # avtool
 
+[![License: MIT](https://img.shields.io/badge/License-GPL_v3-brightgreen.svg)](https://github.com/clok/avtool/blob/main/LICENSE)
+[![Go Report Card](https://goreportcard.com/badge/clok/avtool)](https://goreportcard.com/report/clok/avtool)
+[![Coverage Status](https://coveralls.io/repos/github/clok/avtool/badge.svg?branch=main)](https://coveralls.io/github/clok/avtool?branch=main)
+[![go.dev reference](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white)](https://pkg.go.dev/github.com/clok/avtool/v2?tab=overview)
+
 > NOTE: Original code written by [@pbthorste](https://github.com/pbthorste) for [https://github.com/pbthorste/avtool](https://github.com/pbthorste/avtool)
 >
 > HUGE SHOUT OUT to [@pbthorste](https://github.com/pbthorste)