Without the `...` prefix, CUE interprets a type enclosed in square
brackets as a list of exactly one of that type. The ellipsis changes it
to mean a list of any number of that type.
A bunch of stuff that wasn't schema definitions ended up in the `schema`
package. Rather than split values up in a bunch of top-level packages,
I think it would be better to have a package-per-app model.
