feature parity: owner metadata key in package.json

[technicalpickles]

@alexevanczuk pointed this out to me, and gave it a whirl on our monolith. With this version, I'm seeing a ton of error for files like:

$ codeowners validate

Some files are missing ownership:
- frontend/javascripts/packages/blabhblahblah/index.tsx

$ bin/codeownership validate
$

When I run codeowners generate, the diff ends up deleting a bunch of items in a line section titled: Owner metadata key in package.json

[technicalpickles]

https://github.com/rubyatscale/code_ownership/blob/main/lib/code_ownership/private/ownership_mappers/js_package_ownership.rb for reference

[technicalpickles]

I think #19 fixed this ... or was otherwise fixed at some point.