Enable public access to the Vercel live preview

[jamesread]

Hey @nevo-david , is it possible to enable public guest access to the Vercel live preview?

It would be important to require contributor permission before allowing Vercel builds though - don't want people using this to publish any old junk.

[jamesread]

Vercel seems to be a bot, rather than a standard GitHub Action. This is where we'd set the permission if it was a GitHub action;