chore(python): add .github/CODEOWNERS as a templated file

synthtool/gcp/templates/python_library/.github/CODEOWNERS

@@ -0,0 +1,19 @@
+# Code owners file.
+# This file controls who is tagged for review for any given pull request.
+#
+# For syntax help see:
+# https://help.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners#codeowners-syntax
+# Note: This file is autogenerated. To make changes to the codeowner team, please update .repo-metadata.json.
+{% if metadata['repo']['codeowner_team']|length %}
+# @googleapis/yoshi-python {{ metadata['repo']['codeowner_team'] }} are the default owners for changes in this repo
+*     @googleapis/yoshi-python {{ metadata['repo']['codeowner_team'] }}
+
+# @googleapis/python-samples-owners {{ metadata['repo']['codeowner_team'] }} are the default owners for samples changes
+/samples/   @googleapis/python-samples-owners {{ metadata['repo']['codeowner_team'] }}
+{% else %}
+# @googleapis/yoshi-python is the default owner for changes in this repo
+*     @googleapis/yoshi-python
+
+# @googleapis/python-samples-owners is the default owner for samples changes
+/samples/   @googleapis/python-samples-owners
+{% endif -%}