readme: add github actions badge

README.md

@@ -1,6 +1,7 @@
 srsRAN
 ======
 
+[![Build Status](https://github.com/srsran/srsRAN/actions/workflows/ccpp.yml/badge.svg?branch=master)](https://github.com/srsran/srsRAN/actions)
 [![Build Status](https://app.travis-ci.com/srsran/srsRAN.svg?branch=master)](https://app.travis-ci.com/github/srsran/srsRAN)
 [![Language grade: C/C++](https://img.shields.io/lgtm/grade/cpp/g/srsran/srsRAN.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/srsran/srsRAN/context:cpp)
 [![Coverity](https://scan.coverity.com/projects/23045/badge.svg)](https://scan.coverity.com/projects/srsran)