Fix types

[tommy-mitchell]

Fixes #62.

I've gone through https://github.com/npm/registry/blob/master/docs/responses/package-metadata.md and updated the registry types to match (though it seems a little outdated, see https://docs.npmjs.com/about-registry-signatures or npm/registry#24). I've also updated the return type of packageJson to match the options provided.

Type tests are failing due to a tsd issue, need to make a PR to add an error code.

[tommy-mitchell]

Did some manual testing of outputs and added a few more undocumented fields. Think this is good for review.

Not sure what's up with the failing CI, I can't reproduce the errors locally.

[tommy-mitchell]

Think I figured it out - packageJson({fullMetadata: false}) returns FullVersion, which has [key: string]: unknown:

Not sure why that wasn't resolving like that locally for me, though.

[tommy-mitchell]

Another missing tsd code (tsdjs/tsd#211):

Found an error that tsd does not currently support (ts18046)

I didn't even realize they went that high.

[tommy-mitchell]

Tests are passing now!

[tommy-mitchell]

@sindresorhus this was my last PR :)