Extends Config/Plugin for Deno packaging

[AndresPrez]

Tackles the oclif/core part for https://github.com/oclif/core/issues/503.

It paves the way to start supporting deno projects. It essentially extends the logic around using the package.json as the project's root config file to also support Deno's deno.jsonc configuration file.

[salesforce-cla[bot]]

Thanks for the contribution! Before we can merge this, we need @AndresPrez to sign the Salesforce.com Contributor License Agreement.