feat: loading featurizer

[FMcil]

Hi Kevin!

I added a featurizer that calculates uptake values based on RASPA.

It is heavily based on the Henry featurizer. I would very happy if someone could check over the RASPA simulation script in loading.py before this is pull request is accepted.

The simulation script is based on an example in the RASPA2 repo.

FYI I received multiple fails in tox unrelated to this change. There were no issues using pytest on test_henry.py and test_loading.py

[kjappelbaum]

Thanks for this addition and sorry for the long delay in reviewing it!