Support dependency of idna 6.0.0

[garte]

Your dependency rule states that you do only support idna < 6.0.0 which clashes with hackney which requires 6.0.0: https://hex.pm/packages/hackney

This makes it impossible to have both packages running at the same time. Is there a way to fix this?

[axelson]

@garte this is supported on my fork: https://github.com/axelson/publicsuffix-elixir