Add @cfworker/json-schema

[jdanyow]

@cfworker/json-schema is a validator that does not use code generation (eval or new Function). It's compatible with drafts 4, 7, and 2019-09.

eval and friends are not available in Cloudflare Workers so ajv style validators can't be used with dynamic schemas. The other non-code-generating validators are pretty out of date with the latest spec so I created yet another validator 🙄

This PR:

1. Adds support for scoped packages in testRunner.js
2. Makes minimal changes to index.js to support modern type: module packages.
3. Adds @cfworker/json-schema to the list of validators

I'm sure changes will be required, I tried to use a light touch when making the module support changes.

Depending on your version of node you'll need to add some command line arguments to enable module support. I'm using v13.13.0.

node --experimental-modules --es-module-specifier-resolution=node index.js

Thanks for putting this benchmark together by the way, it's been super helpful for myself and the community.