Automatically add external_links to all services to enable access to domains in the web container

[jonhattan]

No description provided.

[juanjol]

While I like the idea of adding external_links automatically, I see a problem with having a dependency on Python. The main premise of Aljibe is not needing to have anything installer on the host beyond docker and ddev, not even composer or php, so adding a dependency with python is totally out of scope. We have to work along these lines but adapt the script to bash or sh.