-ws option only works on windows and linux with gnome

Investigate wether the -wsz option can be implemented via stellarium sreenshots with a user defined size as suggerted here:
https://github.com/Stellarium/stellarium/discussions/3638#discussioncomment-8620912

In a nutshell:

- create an ini file in the temp folder based on the user ini file and define the desired screenshot size therein
- start stellarium with that ini file