What problem does this solve or what need does it fill?

Add the ability to ignore a field of a bundle using the #[derive(Bundle)] macro, causing it to not be included in the generated list of components.

This is primarily useful when working with PhantomData.

What solution would you like?

#[derive(Bundle)]
struct GenericBundle<T>{
 transform: Transform,
  #[bundle(ignore)]
  _phantom: PhantomData<T>,
}

Modify the derive Bundle macro to accomplish this :)

Be sure to add this to the Bundle docs as a doc test so this keeps working and can be discovered.