Add cobertura code coverage to github actions

Author: tdebatty

.github/workflows/maven.yml

@@ -23,3 +23,5 @@ jobs:
         distribution: 'adopt'
     - name: Build with Maven
       run: mvn -B package --file pom.xml
+    - name: Compute code coverage
+      run: mvn -B clean cobertura:cobertura coveralls:report --file pom.xml