NEXT: Contributor component documentation should cover Zag.js integration

[endigo9740]

Link to the Page

https://next.skeleton.dev/docs/resources/contribute/components

Describe the Issue (screenshots encouraged!)

Following our recent integration of Zag.js, we should review the Skeleton v3 component contribution documentation adequately reflects the process for integrating Zag-base components.

Goals

• Briefly explain the purpose and benefits of Zag
• Explain what components should or should not use Zag
• Link to the Zag.js documentation: React (website), Svelte (repo)
• Provide a quick walkthrough of the integration process
• Note how Zag package versions are controlled via PNPM catalogs

NOTE: consider recording a video tutorial for this process