**Description** Implementing regridding as a separate utility function and add pyrho as an optional dependency. **Solution** This can be done with the `monty.dev.requires` decorator like [here](https://github.com/Quantum-Accelerators/quacc/blob/5efd46887acf71ab9a3929566feeb199b003d5d8/src/quacc/recipes/psi4/core.py#L24).
