add `npm view .`

Fixes #5520

This adds back the ability to run `npm view .`. If a package.json
exists in the cwd, it reads it to get the name and author. It fetches
the package from the registry. If the local package.json has an author
field, it validates that the author of the local package matches the
author of the fetched package.

Includes multiple tests for `npm view`
This seems like an unnecessary piece for this particular change. Extract this and file it as a separate PR (because I think it needs a little more bikeshedding so we can come up with the least surprising behavior), make @isaacs's other suggested changes, and I'll merge this PR in.