Add `bytemuck` attribute to `NoUninit` derive

[richardpringle]

Not sure if you didn't add this attribute here for a reason, but it works perfectly for re-exporting the crate when you do

(I can also add the attribute to the other proc_macro_derives if you'd like).

[Lokathor]

Normally I'd let fu5ha make all final approvals on proc-macro changes, but since this is already used in other places within the derives crate I'll just merge this small change now.

[richardpringle]

Thanks @Lokathor (for both the merge and the crate)!