Fail PR checks on broken internal links

[porridge]

What would you like to be added:

A GitHub required check that prevents merging If there is a broken link that points within the kudo.dev site.

Why is this needed:

While #231 is a great improvement, it is easy to miss a mere warning:

• there are some false-positives cloud the vision somewhat,
• in a typical make docker-run the screen is automatically cleared soon after the warnings are shown, hiding them from view
• there is no visibility into the warnings for a reviewer