Improve installation instructions for MacOS

[jeremiahrose]

I found that installation on MacOS was far from straightforward and it took me more than an hour of troubleshooting to get it working. Documenting all of the extra steps required will help people in future.

1. The conda-forge channel was required in order to create the virtual environment: conda config --append channels conda-forge
2. QT5 needs to be installed system wide:brew install qt5
3. qmake executable needs to be available on the system path: brew link qt5 --force
4. Installing PtQt5 from requirements.txt does not work because it hangs on a license acceptance step. This can be circumvented with pip install PyQt5==5.15.9 --force-reinstall --config-settings --confirm-license= --verbose
5. Then the rest of the dependencies can finally be installed: pip install -v -r "requirements.txt"

[JorgeMaker]

Hi @jeremiahrose,

Thank you for your collaboration! I’m currently a bit busy, but if you’d like to create a Pull Request updating the MD file that describes the installation process to include all the necessary steps for a correct installation on macOS, I’d be more than happy to review and approve it.

Best regards! 😊