Add platformdirs

[adament]

Platformdirs is a fork of appdirs and has replaced appdirs in zeep and black.

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[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/platformdirs) and found it was in an excellent condition.

[adament]

@gaborbernat Would you be willing to help maintain the conda package for platformdirs? It is mostly keeping the dependency and license information in the conda package up to date. If so I will add you to the recipe-maintainers list.

@conda-forge/help-python I think this recipe is ready for review.

[gaborbernat]

Sure 😊