Generate README.md files with 11ty

[LeaVerou]

Currently we have data about backends that we have to maintain in several different places just so we could have reasonable READMEs. If we generated the READMEs we could generate them from data that is stored in one place (e.g. together with the bakend, as a sort of manifest file) or even the backends themselves, by having JS data files that import the backends and read their properties!

The downside would be that we'd need to commit build artifacts to the repo (the README files) but I think that's acceptable.

[LeaVerou]

I was thinking the file could be as simple as meta.json containing a structure like:

{
	name: "GitHub Files", // auto-generated if not present
	description: "Write & read data and upload files to GitHub repositories. Create GitHub repositories as needed",
	can: { read: true, write: true, uploads: true, login: true }
}

Parents & children would be determined from URL structure.