Add support for using github workflow_run event type as a trigger

[ssbarnea]

Based on documentation, currently only push and pull_request events from github are supported.

As I do want to trigger a pipeline when a github scheduled workflow fails, I need to be able to react on workflow_run event type, while filtering by payload with action=='completed' && workflows_run.name == 'jobname' && workflow_run.conclusion != 'success'.

If I understand correctly this is not supported right now.

[chmouel]

This is indeed not supported at the moment,

[martindbrv]

I would like to implement this feature, so can I get assigned @chmouel?