Shared "template" Notebooks/Collections feature

[vcavallo]

relies on #28

Once pushing to and pulling from an external source is possible (#28), then we could add shareable "template" resources:

A user could create a notebook or collection - perhaps a template for a knowledge base, or a static list of mental health resources for new groups to start with, whatever people might need - then export this set of resources to S3 and create an instance of a (new concept to be built) Shared Collection and optionally whitelist some ships.

Long ago we had discussed a kind of "automated onboarding" that would allow someone to start a group for X concern (the example at the time was local LGBTQ support groups). By installing Peat and subscribing to some known Shared Collection, a newly-formed entity that wishes to provide these resources could do so by importing from said Shared Collection.
Perhaps the "installing Peat and subscribing..." process could even be automated in a custom pill...