[setup.py] use trove classifiers for supported operating systems
[setup.py] use trove classifiers for supported operating systems

This ensures that PyPi users can programmatically locate pyroSAR as an project
supported on Linux and Windows operating systems.

For example: https://pypi.org/search/?c=Operating+System+%3A%3A+POSIX+%3A%3A+Linux

This is suggested as best practice in the Python Packaging User Guide.

johntruckenbrodt/pyroSAR,johntruckenbrodt/pyroSAR