buildSubcontextInitialAction
inline fun buildSubcontextInitialAction(block: MutableList<CustomBehaviourContextAndTypeReceiver<BehaviourContext, Unit, Update>>.() -> Unit): CustomBehaviourContextAndTypeReceiver<BehaviourContext, Unit, Update>
Build CombinedSubcontextInitialAction with block and return callback, which appropriate for BehaviourContext builders with subcontextInitialAction argument