replace travis badge with actions badge

Author: oreoshake

README.md

@@ -1,4 +1,4 @@
-# Secure Headers [![Build Status](https://travis-ci.org/twitter/secure_headers.svg?branch=master)](http://travis-ci.org/twitter/secure_headers) [![Code Climate](https://codeclimate.com/github/twitter/secureheaders.svg)](https://codeclimate.com/github/twitter/secureheaders) [![Coverage Status](https://coveralls.io/repos/twitter/secureheaders/badge.svg)](https://coveralls.io/r/twitter/secureheaders)
+# Secure Headers ![Build + Test](https://github.com/github/secure_headers/workflows/Build%20+%20Test/badge.svg?branch=master)  [![Code Climate](https://codeclimate.com/github/twitter/secureheaders.svg)](https://codeclimate.com/github/twitter/secureheaders) [![Coverage Status](https://coveralls.io/repos/twitter/secureheaders/badge.svg)](https://coveralls.io/r/twitter/secureheaders)
 
 **master represents 6.x line**. See the [upgrading to 4.x doc](docs/upgrading-to-4-0.md), [upgrading to 5.x doc](docs/upgrading-to-5-0.md), or [upgrading to 6.x doc](docs/upgrading-to-6-0.md) for instructions on how to upgrade. Bug fixes should go in the 5.x branch for now.