feature request: sharing collections

[EVALGroup]

It would be nice to be able to share an entire collection, where any drawings you add or remove is visible to everyone that has access to the collection. Not having to share each drawing individually.

[ZimengXiong]

Implementation attempt in #120, but I do not want to move that whole PR forward in its current shape. feature is still on the roadmap, and the next step is a follow-up on #120, if there is none, I'll pick it up.