0.5.0

Added

• Classify custom and inner drop behavior through RustSpec::Drop.
• Support #[rust_spec(custom_drop)] with compile-time checks.

Fixed

• Reject #[rust_spec(with_custom_niche) on enums and unions.

Changed

• Rename #[rust_spec(with_custom_niche)] to #[rust_spec(custom_niche)].