Test `superstruct` against current major version

[blimmer]

Today, the test suite runs against superstruct 0.15.x:

However, the current major version is 2.x. It would be nice to test against the current major version so people could be confident in updating.

Further, it's probably a good idea for joist's package.json to specify superstruct as an optional peer dependency, with the supported version(s). You can use the peerDependenciesMeta option to specify optional peerdeps.

[stephenh]

I tried bumping to 2.x and am getting errors that it is ESM-only, although afaict that's not intentional on their side:

https://github.com/ianstormtaylor/superstruct/issues/1287

A recent development in the runtime types space is:

https://standardschema.dev/

Which, if Joist supported, in theory we could remove superstruct & zod & ...specific lib support..., and instead generically support any runtime library that supported standardschema.

The biggest downside to us tactically is that superstruct doesn't support standardschema yet:

https://github.com/ianstormtaylor/superstruct/issues/1291

So we'd probably end up needing to move to zod or Arktype.