For perf reasons, it is more efficient to not rely on creating an `URL` object. Instead we check for the explicit protocol to detect external links.
This will also force us to use relative links, so archived versions & next versions navigate on the current version of the site.
fixes#58954
PR Close#58955
To increase the ease of development we are moving @angular/docs into the adev directory within this repo. While
we are doing this to improve our development experience in the short term, efforts are also in place
to maintain a division between this @angular/docs (shared) code and adev itself, so that it can be extracted
back out in the future when components is ready to leverage it as well.
PR Close#57132
