What are some gotchas when using bevy_ecs without bevy_app?

[navneetankur]

From a look at documentation I found two.

1. Remember to call Events::update exactly once per update/frame.
2. Remember to call World::clear_trackers once per frame.

Is there anything else? Or are these things listed somewhere already. I can't possibly read and remember the whole bevy_ecs doc.

[NiklasEi]

Not specific to usage without bevy_app, but one surprise for using bevy_ecs outside of Bevy: I wanted to reexport bevy_ecs so that users of my library don't have to keep their version in sync. But the derive macros (for Component, Resource and so on) do not support that.
See #9831