Update README.md by adding a failure handler script

[erikauer]

In this docs you find an example how to retry an task using an additional releaseVariable: https://docs.xebialabs.com/v.10.1/release/how-to/task-failure-handler/#disabling-the-feature

In case you have a lot of parallel tasks you would need to create a releaseVariable for each task.

So I add an example using tasks.failuresCount which allows you to create no releaseVariables.