add recipe to build pywatershed package

[jdhughes-usgs]

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[conda-forge-webservices]

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

I wanted to let you know that I linted all conda-recipes in your PR (recipes/pywatershed) and found some lint.

Here's what I've got...

For recipes/pywatershed:

• Failed to even lint the recipe, probably because of a conda-smithy bug 😢. This likely indicates a problem in your meta.yaml, though. To get a traceback to help figure out what's going on, install conda-smithy and run conda smithy recipe-lint . from the recipe directory.

[conda-forge-webservices]

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/pywatershed) and found it was in an excellent condition.

[wpbonelli]

Willing to be a listed maintainer.

[jmccreight]

I will be a maintainer. Thanks

[jdhughes-usgs]

@conda-forge/help-python, ready for review!