0.6.0

• All indices are now usize (previously some were i32 which lead to inconsistent APIs)
• Events are nicer to work with using the new AnimationEvent enum
• Skeleton::set_skin and Skin::add_skin marked unsafe (with safety comments)
  • Add Skeleton::set_skins_by_name as a safe alternative for the primary use case (conglomerate skins)
• New error type: SpineError::PathNotUtf8 (removes some internal unwrap calls)
• Lots of clippy fixes
  • Many functions now marked #[must_use]
• The following functions are no longer unsafe:
  • MeshAttachment::new_linked_mesh
  • MeshAttachment::update_region
  • RegionAttachment::update_region
• Upstream fixes
  • Fix IK constraint NaN when a parent bone has zero scale
  • Handle skeleton loading problems without crashes (EsotericSoftware/spine-runtimes#2276)
  • Fix crash when skeleton hash or spine doesn't exist in JSON file (EsotericSoftware/spine-runtimes#2270)
  • Fix integer values in events broken with binary loader (EsotericSoftware/spine-runtimes#2281)