Inference dependencies

[aditya0by0]

changes as per ChEB-AI/python-chebai#114 (comment)

[sfluegel05]

descriptastorus is needed for creating datasets, right? I would put that under dependencies (as it is not just used for development)

[aditya0by0]

The main dependencies should have only packages required to inference of the model. Hence, "descriptastorus" is placed under optional dependency as its not needed for inference but used during dataset creation.

[sfluegel05]

Then we should follow the approach from #114 and differentiate between training and linters

[sfluegel05]

I moved descriptatorus back to the mandatory dependencies - we need this for inference (calculating the properties of new molecules)

I made some unrelated changes to the readme, descriptatorus is added in PR #26