Resource replication

[Shatur]

Should be simple to add. Maybe we make it similar to components, except there are no groups.
We will need support write callbacks and writing into a separate resource for history (until we get resources as entities and can attach the history to the resource entity).
If people replicate resources there will definitely end up being some that need rollback.

[ironpeak]

This would be very useful to me, even without having rollbacks. I just need the ability for the server to create a resource and it being synced to the clients.

[Shatur]

Resources will become entities soon: bevyengine/bevy#17485
Our current implementation will just start working for resources as well. For now, I would suggest using singleton entities as a temporary workaround 🙂