CI: show badge of recent build

README.md

@@ -6,6 +6,7 @@
 ---------
 
 [![GitHub release](https://img.shields.io/github/release/calamares/calamares.svg)](https://github.com/calamares/calamares/releases)
+[![GitHub Build Status](https://img.shields.io/github/workflow/status/calamares/calamares/ci?label=GH%20build)](https://github.com/calamares/calamares/actions?query=workflow%3Aci)
 [![Travis Build Status](https://travis-ci.org/calamares/calamares.svg?branch=calamares)](https://travis-ci.org/calamares/calamares)
 [![Coverity Scan Build Status](https://scan.coverity.com/projects/5389/badge.svg)](https://scan.coverity.com/projects/5389)
 [![GitHub license](https://img.shields.io/github/license/calamares/calamares.svg)](https://github.com/calamares/calamares/blob/calamares/LICENSE)