Function LifecycleEffect 

pub fn LifecycleEffect<K: PartialEq + 'static>(
    keys: K,
    observer: impl FnMut(LifecycleEvent) + 'static,
)

Registers a lifecycle observer for the lifetime of the current composition.

Screens that only need the current state read cranpose_services::local_lifecycle_state instead; this is for work that must react to a transition.