chore(workflow): rework release and prerelease workflows

[gcornut]

General summary

Split release and prerelease workflows

• "Prerelease workflow" is manully triggered and pushes to NPM without PR or tag
• "Prepare release workflow" is manually triggered and only opens a PR with version incremented
• "Publish Release Workflow" is triggered when merging the release commit on master and triggers publish on NPM, chromatic, docker, etc.

Test

It's difficult to test these because we can't trigger manual workflow from a PR but we can stub some parts and run other parts on PR push

• Test Prerelease Workflow ✅ (run, stub commit)
• Test prepare release
  • Fail if not on master ✅ (run, stub commit)
  • Else increment version and create PR ✅ (run, stub commit)
• Test publish release
  • Skip if not a release commit ✅ (run, stub commit)
  • Build & push NPM, release note, demo site docker, etc. ✅ (run, stub commit)

[hchevallier]

LGTM

[gcornut]

Test OK deploy demo site ✅