Document how to navigate to a document after executing a designer action

Using Designer configuration, it is possible to navigate to a specific document after executing a chain.

This is not documented for now although it is a recurrent need.

Example config:
Event field: navigate
Detail field: {"doc": {"path": "/default-domain"}}

Only works with static paths for now, not dynamic ones. See https://app.prodpad.com/feedback/6a84b160-5069-11e9-9453-e5baf14f2970/canvas for follow up on this.