Add support for namespace packages. Closes jaraco/skeleton#40.

Author: jaraco

setup.cfg

@@ -15,12 +15,18 @@ classifiers =
 	Programming Language :: Python :: 3 :: Only
 
 [options]
-packages = find:
+packages = find_namespace:
 include_package_data = true
 python_requires = >=3.6
 install_requires =
 setup_requires = setuptools_scm[toml] >= 3.4.1
 
+[options.packages.find]
+exclude =
+        build*
+        docs*
+        tests*
+
 [options.extras_require]
 testing =
 	# upstream