Add skip-existing option to PyPI publish step in CD workflow

Author: rbeucher

.github/workflows/cd.yml

@@ -30,6 +30,8 @@ jobs:
 
       - name: Publish package to PyPI
         uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          skip-existing: true
 
   conda:
     name: build and deploy to conda (${{ matrix.os }})