Need to add `enthalpy is TOTEN` to `pymatgen.io.vasp.outputs` module?

[chunweizhu]

When the calculation of VASP is performed under pressure conditions, the PSTRESS parameter needs to be added to INCAR, and the enthalpy is TOTEN item will be obtained in OUTCAR. Sometimes we need to extract the value of this item, so I wonder if we need to implement this operation to pymatgen.io.vasp.outputs module? I can submit a PR if needed. thanks！