chore: adjust setup.py

Author: gforcada

setup.py

@@ -28,8 +28,9 @@
     author_email="plone-developers@lists.sourceforge.net",
     url="https://github.com/plone/Products.CMFPlacefulWorkflow",
     license="GPL",
-    packages=find_packages(),
+    packages=find_packages("src"),
     namespace_packages=["Products"],
+    package_dir={"": "src"},
     include_package_data=True,
     zip_safe=False,
     python_requires=">=3.8",