/// Helper macro for creating an array of boxed actions.
///
/// ```rust,no_run
/// # use bevy_ecs::prelude::*;
/// # use bevy_sequential_actions::*;
/// #
/// # struct EmptyAction;
/// # impl Action for EmptyAction {
/// # fn is_finished(&self, _a: Entity, _w: &World) -> bool { true }
/// # fn on_start(&mut self, _a: Entity, _w: &mut World) -> bool { true }
/// # fn on_stop(&mut self, _a: Option<Entity>, _w: &mut World, _r: StopReason) {}
/// # }
/// #
/// # let action_a = EmptyAction;
/// # let action_b = EmptyAction;
/// #
/// let actions: [Box<dyn Action>; 3] = actions![
/// action_a,
/// action_b,
/// |agent: Entity, world: &mut World| -> bool {
/// // on_start
/// true
/// },
/// ];
/// ```