is-core-module is missing core.json

[jimsimon]

I'm trying to run this tool against a fairly large project and noticed that the recently added is-core-module package doesn't include core.json. It looks like a bunch of fairly common projects rely on this file directly via an import or via a CLI command.

I see references from older versions of resolve and prettier. I'll see if updating those packages helps, but it might not hurt to add this file in some fashion to support projects on older versions of dependencies that rely on it.