[-] added license badge

Author: bnkamalesh

README.md

@@ -5,6 +5,7 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/naughtygopher/errors)](https://goreportcard.com/report/github.com/naughtygopher/errors)
 [![Coverage Status](https://coveralls.io/repos/github/naughtygopher/errors/badge.svg?branch=master)](https://coveralls.io/github/naughtygopher/errors?branch=master)
 [![](https://awesome.re/mentioned-badge.svg)](https://github.com/avelino/awesome-go#error-handling)
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://github.com/creativecreature/sturdyc/blob/master/LICENSE)
 
 # Errors v1.0.0