Suggestion: Make 'Spawner' a sub-checkbox of a model

Not completely sold on this, but wondering if it would make sense to have 'spawner' be a property of a model object in Spoke. I'm retroactively updating a scene to have spawners for some of my models so people could grab a copy of them, but I have to copy the properties over manually. I wonder if it would make sense to have them be a single element?

The issue does not name any files, tests, or entry points. Start by locating how model objects and spawners are represented in Spoke, then determine whether combining them is feasible and what the expected editing behavior should be. Done requires an agreed design and an implementation plan, but the issue alone does not define that outcome.

Written by the indexing model from the issue text.