Access e0_dict with the right units

[shenoynikhil]

Accessing the isolated atom energy dict with the right units is currently not straightforward,

from openqdc.utils.units import get_conversion
convert_fn = get_conversion("hartree", ds.__energy_unit__) 
e0_dict = {k:convert_fn(v.mean) for k,v in self.ds.e0s_dispatcher.e0s_dict.items()}

Why need this?

Networks like MACE require access to an e0 dictionary for normalization.