Add ci badge in the readme

README.md

@@ -1,5 +1,7 @@
 # Docker API
 
+![](https://github.com/docker/api/workflows/Continuous%integration/badge.svg)
+
 ## Dev Setup
 
 To setup a development machine to update the API protobufs, first run the  `./setup-dev.sh` script to install the correct version of protobufs on your system and get the protobuild binary.