[frontend] Start page where different apps can be selected
If the app is used as a demonstrator, it would be nice if on the start page you could first select the app (maybe by clicking on the app (thumbnail + short descrp/title) and the select the case with a dropdown menu (current SelectSimulation view).
If there is only one app, we could automatically skip the start page and go to the SelectSimulation view.
This also requires one additional json file in the backend that lists all the apps (which are itself json files like the current simulations.json).