add GHA status badge; remove travis config and scripts (#128)

Author: dgrove-oss

.travis.yml

@@ -19,8 +19,7 @@
 
 # Apache OpenWhisk runtimes for PHP
 [![License](https://img.shields.io/badge/license-Apache--2.0-blue.svg)](http://www.apache.org/licenses/LICENSE-2.0)
-[![Build Status](https://travis-ci.com/apache/openwhisk-runtime-php.svg?branch=master)](https://travis-ci.com/github/apache/openwhisk-runtime-php)
-
+[![Continuous Integration](https://github.com/apache/openwhisk-runtime-php/actions/workflows/ci.yaml/badge.svg)](https://github.com/apache/openwhisk-runtime-php/actions/workflows/ci.yaml)
 
 ## PHP versions