Emit scaladoc for package private classes

[Jasper-M]

If I want to find out where the validNel extension method is coming from, one option is to search for it in the scaladoc. I will find https://typelevel.org/cats/api/cats/syntax/package$$validated$.html and https://typelevel.org/cats/api/cats/syntax/ValidatedIdSyntax.html. Mystery solved.

If however I'm looking for validNec I will find nothing because it's in another trait ValidatedIdOpsBinCompat0 which is package private.

Regardless of the reasons and decisions that led to one method sitting in a publicly visible trait and another at least as useful method sitting in an ominously named package private trait, it would be nice if both were equally visible in the scaladoc.