Adds widened has support to ReadonlySet

[Kadrei]

Currently only Set has support for the widened has and if someone would use ReadonlySet they would lose this widening.

With this change ReadonlySet now supports the widened has argument.

I added it directly to the set-has rule to be similair to the handling in array-includes

I assume this should apply to WeakSet as well - if wanted I can add it as well.

[mattpocock]

Makes sense! WeakSet likely also deserves this treatment. Could you also add a changeset? (with pnpm changeset)

[Kadrei]

Just looked at WeakSet and as it only stores objects it does not work with the current WidenLiteral so I will keep it out for now and even would question if the lib should support it.

Added the changeset.