This PR adds a Package.juvix file to the global 'package' package (that
is the package containing the `PackageDescription.{Basic, V1}` modules.
This means that users can now go-to-definition on Package.juvix types
and identifiers and navigate to fully highlighted
`PackageDescription.{Basic, V1}` modules.
* Closes https://github.com/anoma/juvix/issues/2525