If triggered build is from FlowRun type, then iterate through its jobs graph adding all downstream jobs build urls to the message that will be posted to github pull request.

Please review my changes, and consider changing what you think it's better for the plugin. I'm not sure if I could have achieved this in a easier/extensible way, so please send me your feedback about how to do it. Thanks in advance
This needs to be an *optional* dependency. What happens if someone doesn't have this plugin installed? I don't want it to be required to be installed.