Update build status badge in docs

Author: ramsey

docs/index.md

@@ -11,7 +11,7 @@ League/oauth2-client
 [![Source Code](https://img.shields.io/badge/source-thephpleague/oauth2--client-blue.svg?style=flat-square)](https://github.com/thephpleague/oauth2-client)
 [![Latest Version](https://img.shields.io/github/release/thephpleague/oauth2-client.svg?style=flat-square)](https://github.com/thephpleague/oauth2-client/releases)
 [![Software License](https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat-square)](https://github.com/thephpleague/oauth2-client/blob/master/LICENSE)
-[![Build Status](https://img.shields.io/travis/thephpleague/oauth2-client/master.svg?style=flat-square)](https://travis-ci.org/thephpleague/oauth2-client)
+[![Build Status](https://img.shields.io/github/workflow/status/thephpleague/oauth2-client/CI?label=CI&logo=github&style=flat-square)](https://github.com/thephpleague/oauth2-client/actions?query=workflow%3ACI)
 [![Coverage Status](https://img.shields.io/coveralls/thephpleague/oauth2-client/master.svg?style=flat-square)](https://coveralls.io/r/thephpleague/oauth2-client?branch=master)
 [![Total Downloads](https://img.shields.io/packagist/dt/league/oauth2-client.svg?style=flat-square)](https://packagist.org/packages/league/oauth2-client)