Turn project into a CMake project.

[ingomueller-net]

This MR turns the project into a CMake project. The compile-and-run-test still works, but I removed the Makefile to avoid double maintenance. I have also made a small effort to port wsjcpp.yml, but gave up trying to understand how to use that package manager after 15 minutes or so, so I couldn't test if my port actually works. Let me know if you have questions or anything bothers you.