Fallback URLs

This is an experiment looking to see if we can do any better at making URLs that work even when the destination is inaccessible. In particular, some misuse of the data URL scheme provides some interesting possibilities for fmaking URLs that have more intelligence than just a resource locator. A longer description is at the link below, but for reference, most browsers can access this page as:

Try sending your friends here, or visiting in another browser through this page's sharable URL.

For more information on http+ URLs, see the explanation at http+.md