[riccardobl]

This PR improves the gltf loader to support more than one attachment per bone

[jaime-jmebot]

Hi @riccardobl, thanks for submitting this pull request!

Overview

This change resolves an issue in GltfLoader where glTF joint nodes containing multiple attached child spatials would only retain the last attached spatial, discarding any preceding ones.

Technical Discussion

• GltfLoader: Converting the single attachedSpatial field on JointWrapper into a List<Spatial> (attachedSpatials) allows findChildren() to accumulate all non-joint child spatials attached to a bone. During setupControls(), all attached spatials are iterated over and safely added to the corresponding AttachmentsNode on the SkinControl.
• Test Coverage: The added unit test (keepsEverySpatialAttachedToTheSameJoint) along with JointAttachments.gltf verifies that multiple attachment nodes on a single joint survive glTF import and remain reachable via scene traversal.

Everything is neatly structured, correct, and well-tested. Great improvement for glTF support!