[Remove Node.js] Setup JS dependencies using CDN and import maps

[malparty]

inherit #431

Note

This issue does NOT include any code change in the Rails template (yet), as these will be based on the RFC results.

Why

JS dependencies are currently managed with yarn (which uses Node.js).

Checklist

• POC in CX (side branches)
• Presentation of learnings
• RFC in GitHub discussion

Insight 📝

WIP

Who Benefits?

• Developers for the knowledge
• Future clients' projects for improved tooling decisions.