Support for AM1BCC charge

[xiki-tempula]

Would it be good to support AM1BCC charge for both fragment and whole molecule?
The charge could be generated from a rdkit mol using OpenFFMol with

openffmol.from_rdkit(rdmol)
openffmol.assign_partial_charges("am1bccelf10")

But would need to add openff-toolkit as a new dependency. This calculation is quick and can be done as part of the QForce routine.

[selimsami]

I would like to avoid adding that dependency just for this. Openff-toolkit seem to have a ton of dependencies, one of which being the huge rdkit (~100 MB).

AM1 charges you could probably get from any software - I imagine there should be an simple way to get the BCC correction?