[Users] CarpetX tutorial

[Steven Brandt]

Thanks again to Erik for presenting the first official CarpetX tutorial.

You can find the recording here: 
https://lsu.zoom.us/rec/share/YcrCqkVkEZ5BjqZrXQa-vt7EOGyXFL8rD26-GASPOEhSYvscG3AAEIShRuIM9FD4.p2KUW93Ytojr6L8V

Also, inside the cactusamrex repo, there are dockerfiles to create a 
working CarpetX image.

You can find the working image at this location on dockerhub: 
einsteintoolkit/cactus-amrex-jovyan

Invoking "build.sh" inside the image should check out (using 
GetComponents) and build Cactus with CarpetX.

--Steve