Replace Travis with Github Actions badge

Author: martin-helmich

README.md

@@ -1,6 +1,6 @@
 # PSR-7 assertions for PHPUnit
 
-[![Build Status](https://travis-ci.org/martin-helmich/phpunit-psr7-assert.svg?branch=master)](https://travis-ci.org/martin-helmich/phpunit-psr7-assert)
+![Unit tests](https://github.com/martin-helmich/phpunit-psr7-assert/workflows/Unit%20tests/badge.svg)
 [![Code Climate](https://codeclimate.com/github/martin-helmich/phpunit-psr7-assert/badges/gpa.svg)](https://codeclimate.com/github/martin-helmich/phpunit-psr7-assert)
 [![Test Coverage](https://codeclimate.com/github/martin-helmich/phpunit-psr7-assert/badges/coverage.svg)](https://codeclimate.com/github/martin-helmich/phpunit-psr7-assert/coverage)