cython, python3-dev (or -devel) and libjpeg-dev (or -devel) should be listed as dependencies

[j-hudecek]

Describe the bug
Running setup.py produces colourful errors

The headers or library files could not be found for jpeg,
a required dependency when compiling Pillow from source.

SystemError: Cannot compile 'Python.h'. Perhaps you need to install python-dev|python-devel.

ModuleNotFoundError: No module named 'Cython'

RuntimeError: Running cythonize failed!

To Reproduce
On minimal ubuntu 18.04 run setup.py

Expected behavior
Setup.py should install all dependencies or fail early if it's not possible

Environment
SlideScore Python API version:
How installed: python3.8 setup.py install
Python version: 3.8
Operating System: Ubuntu 18.04

Additional context
Add any other context about the problem here.

[jonasteuwen]

Will fix this.