Create app example project files based on existing notebooks

This is the first step to create App tutorials, which would mirror those done for EasyDiffractionApp. (as in https://docs.easydiffraction.org/app/how-to-use/user-interface/ )

Look at https://docs.easyreflectometry.org/tutorials.html and try to mimic these examples in the app (some functionality is not yet available, so care needs to be taken).
