Create fully-featured CLI for boostrapping new Eleventy projects

[uncenter]

Coming from https://fediverse.zachleat.com/@zachleat/112877708366503480.

Would love to see something more substantial from this, like my https://github.com/uncenter/create-eleventy-app. Lots of other similar projects have tools like this; Hugo has hugo new site, Zola has zola init, Astro has create-astro, Next.js has create-next-app (as well as community versions like https://create.t3.gg/), etc. I know Eleventy tries to stay unopinionated but that same stance also makes it a little unfriendly for people trying to jump right into a basic site.