lack of side-effects examples

[lifeart]

Things I wold like to now how to do in broccoli:

• Async start [https://github.com/broccolijs/broccoli/issues/485]
• Get changed files, found by WatchedDir (live-reload case)
• Postprocess final build (upload artifacts to AEM, for example)
• Get notification once rebuild/build is finished and artifacts saved (side effect to notify developer about updates)
• Have "folder-less" node (for side - effects, load some data to store from server, or by custom logic (not using input))