Insert cards using a jupyer book setup hook

[Zethson]

Currently, we copy the content of the cards to every notebook which not only makes it annoying to keep it in sync, but it also clutters the notebook when downloaded and editing. I propose that we find a way to insert the content just before building the book (or just after it by inserting it into the HTML?). This will require lots of trial and error. Could be a plain Python script that we add to the CI build job or it could be a whole Sphinx extension or ???