Add a built-in Smiles key maker (alongside Inchi / InchiKey )

Add a built-in Smiles key maker (alongside Inchi / InchiKey ): a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). jsonizer = stk.MoleculeJsonizer( key makers=(stk.Inchi(), stk.InchiKey()), )