Mention GDK setup in duo workflow docs

Sebastian Rehmrequested to merge
bastirehm-mention-gdk-setup-duo-workflow into master

What does this MR do and why?

There is a much easier GDK setup available for Duo workflow which often get's missed because it is not mentioned here.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Merge request reports