Add PEP-561 type-support marker (#152)

This will tell mypy and other tooling that this package is typed and
that the types in this library (when present) should be used.

Author: nemacysts

service_configuration_lib/py.typed

@@ -24,6 +24,9 @@
     author='Yelp Compute Infrastructure Team',
     author_email='[email protected]',
     packages=find_packages(exclude=['tests', 'scripts']),
+    package_data={
+        'service_configuration_lib': ['py.typed'],
+    },
     install_requires=[
         'ephemeral-port-reserve >= 1.1.0',
         'PyYAML >= 5.1',