registerExternalAnimation
abstract fun registerExternalAnimation(key: Key, isRunning: () -> Boolean): ExternalAnimationRegistration
Registers an animation outside the item animation that must finish before key can be removed from rendering. Multiple registrations for one key are all observed.
The caller owns the returned registration and must unregister it when the external animation leaves composition or should no longer retain the item. isRunning must read observable Compose snapshot state so changes can resume a suspended item animation.