Add some missing reflect attributes

[mrchantey]

Objective

• Some types are missing reflection attributes, which means we can't use them in scene serialization etc.
• Effected types
  • BorderRadius
  • AnimationTransitions
  • OnAdd
  • OnInsert
  • OnRemove
• My use-case for OnAdd etc to derive reflect is 'Serializable Observer Components'. Add the component, save the scene, then the observer is re-added on scene load.

#[derive(Reflect)]
struct MySerializeableObserver<T: Event>(#[reflect(ignore)]PhantomData<T>);

impl<T: Event> Component for MySerializeableObserver<T> {
  const STORAGE_TYPE: StorageType  = StorageType::Table;
    fn register_component_hooks(hooks: &mut ComponentHooks) {
      hooks.on_add(|mut world, entity, _| {
        world
          .commands()
          .entity(entity)
          .observe(|_trigger: Trigger<T>| {
            println!("it triggered etc.");
          });
    });
  }
}

Solution

• Add the missing traits

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