feat: spring bones docs

[RocioCM]

Summary

This pull request introduces documentation for "Spring Bones," a new feature that enables dynamic physics for wearable accessories (like hair, earrings, and capes) in Decentraland. It adds a dedicated guide, integrates references to spring bones throughout relevant creator documentation, and explains both the modeling and Builder configuration workflows. The main changes improve clarity and provide step-by-step instructions for creators to add and configure spring bones in their wearables.

Major Additions:

• creator/wearables-and-emotes/wearables/spring-bones.md: Added a full guide detailing what spring bones are, how to set them up in Blender, naming conventions, Builder configuration, parameter explanations, technical glTF extension details, and best practices for common use cases.

Documentation Updates & References:

• SUMMARY.md: Added the new "Spring Bones" guide to the documentation sidebar for easy navigation.
• creator/3d-modeling/3d-models.md: Added a note about the DCL_spring_bone_joint glTF extension and linked to the Spring Bones guide.
• creator/3d-modeling/create-a-rig.md: Introduced a new section explaining how to add spring bones to a rig, including step-by-step modeling instructions and a link to the full guide.
• creator/wearables-and-emotes/manage-collections/uploading-wearables.md: Explained how the Builder detects spring bones and provides a configuration panel for adjusting physics parameters.

Wearable Creation Guidance:

• creator/wearables-and-emotes/wearables/README.md, creating-wearables.md: Added overviews, tips, and export instructions for spring bones, including info hints and best practices for hair and accessories. [1] [2] [3] [4]

These changes together provide a complete workflow for creators to leverage spring bones, from modeling to in-game configuration.

Pending Tasks

• Add final limits and remove TODO.
• Add a demo gif in spring bones section start.