Add new CI badges

Author: yjacolin

README.md

@@ -1,4 +1,6 @@
-[![Build Status](https://ci.camptocamp.com/buildStatus/icon?job=geospatial/docker-qgis-server/master)](https://ci.camptocamp.com/job/geospatial/job/docker-qgis-server/job/master/)
+* master:  ![Continuous integration](https://github.com/camptocamp/docker-qgis-server/workflows/Continuous%20integration/badge.svg)
+* 3.10: ![Continuous integration](https://github.com/camptocamp/docker-qgis-server/workflows/Continuous%20integration/badge.svg?branch=3.10)
+* 3.12: ![Continuous integration](https://github.com/camptocamp/docker-qgis-server/workflows/Continuous%20integration/badge.svg?branch=3.12)
 
 # Docker image for QGIS server