Migration guide corrections

[ilyvion]

The signature of the function you need to pass to App::set_runner has changed and this isn't mentioned at all in the migration guide.

Also, the section "Separate states from core ECS" states

Projects that use bevy_app directly and use states will need to add the bevy_state feature.

but bevy_app has no such feature. I think maybe you meant "that use bevy directly?" (It has a feature with that name)

[BD103]

Thanks for the report! I think the signature likely changed in the AppExit PR, but I'll need to go through the blame to confirm.

As for the second bit, I actually just fixed it yesterday in #1539! :)

[alice-i-cecile]

App::set_runner changes will be due to bevyengine/bevy#9202

[BD103]

App::set_runner changes will be due to bevyengine/bevy#9202

It also appears that bevyengine/bevy#13022 contributed to the breaking change as well. I'm working on a PR for this now.