Serve web content out of Earthstar documents right from the pub

[cinnamon-bun]

Right now pubs do 2 things:

1. Sync with clients using the Earthstar sync protocol
2. Serve a barebones HTML UI for poking around the workspaces

We could add a new mode for serving websites right out of Earthstar documents.

If you visited a URL like, say...

https://mypub.com/gateway/+gardening.123/mywebsite/index.html

then the pub could just serve your HTML files, images, etc directly.

See also: earthstar-project/earthstar#116 Support a publishing use-case

See also: https://github.com/earthstar-project/earthstar-fetch/tree/initial-implementation for URL format ideas

Security issues

We might want to either disable javascript using a content security policy, or make sure there's nothing tricky that can be done with arbitrary javascript in a page.

Right now the pub doesn't even use cookies or authenticate you so there's not much harm you could do. It would be neat if you could publish a full-fledged app this way including its javascript.

We also need Invite-only workspaces so that people can read and help host the data without getting the ability to write to it.