esm: JSON modules no longer experimental
The HTML spec has officially landed JSON Modules and as such I think
we can move them out of the "experimental" status. They will still
be behind the --experimental-modules
flag until the entire esm
implementation moves out of experimental.
Refs: https://html.spec.whatwg.org/#creating-a-json-module-script
/cc @domenic and @littledan to confirm that this respects the spec /cc @nodejs/modules