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Add PHS as a storage option in the model

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#Closes #320. ## Changes proposed in this Pull Request I added three source gpkg files from https://maps.nrel.gov/psh to account for three durations of PHS (8hr, 10hr, 12hr). Each duration has...

### Feature Request I will add the feature to allow adding PSH as a storage option in PyPSA ### Suggested Solution _No response_ ### Additional Info _No response_

`p_nom_min` is negative for some renewables

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### Checklist - [X] I am running on an up-to-date [`pypsa-usa` environment](https://github.com/PyPSA/pypsa-usa/blob/master/workflow/envs/environment.yaml). Update via `conda env update -f envs/environment.yaml` ### Issue exisits on what branch Master ### The Issue I...