update build status badge to use GitHub Actions (#240)

Signed-off-by: Alberto Ricart <[email protected]>

Author: aricart

README.md

@@ -5,7 +5,7 @@ Nkeys use [Ed25519](https://ed25519.cr.yp.to/) to provide authentication of JWT
 
 [![License Apache 2](https://img.shields.io/badge/License-Apache2-blue.svg)](https://www.apache.org/licenses/LICENSE-2.0)
 [![ReportCard](https://goreportcard.com/badge/github.com/nats-io/jwt)](https://goreportcard.com/report/nats-io/jwt)
-[![Build Status](https://travis-ci.com/nats-io/jwt.svg?branch=master)](https://travis-ci.com/github/nats-io/jwt)
+[![Build Status](https://github.com/nats-io/jwt/actions/workflows/go-test.yaml/badge.svg?branch=main)](https://github.com/nats-io/jwt/actions)
 [![GoDoc](https://godoc.org/github.com/nats-io/jwt?status.png)](https://godoc.org/github.com/nats-io/jwt/v2)
 [![Coverage Status](https://coveralls.io/repos/github/nats-io/jwt/badge.svg?branch=main)](https://coveralls.io/github/nats-io/jwt?branch=main)
 ```go