Manage shapes using collections

[atapas]

Discussed in https://github.com/TryShape/tryshape/discussions/78

^{Originally posted by atapas July 7, 2021} When user like a shape and make private, there should be a way to collect shapes into their collection so that they can go back to it time to time. A collection can be created, deleted, updated. The underlying shapes in a collection should be unaffected.