Expose p2p URLs publicly if site is public

[RangerMauve]

There's potential for widgets that folks can embed on their sites to link to the p2p version of their site.

• change GET on site API to return just the p2p URLs of a site if public is true.
• Add JS snippet that pulls this data to docs (maybe a custom element?)

[fauno]

@RangerMauve we'll need this to show people their URLs during onboarding!

[RangerMauve]

Nah during onboarding we'll have a token so we can fetch the URLs using the existing API

[fauno]

what i ended up doing during onboarding is just generating the urls with scheme://domain locally