process: add yoshi-python group to CODEOWNERS (#466)

Author: plamut

.github/CODEOWNERS

@@ -5,8 +5,8 @@
 # https://help.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners#codeowners-syntax
 
 
-# The @googleapis/api-pubsub is the default owner for changes in this repo
-*               @googleapis/api-pubsub
+# The @googleapis/api-pubsub and yoshi-python are the default owners for changes in this repo
+*               @googleapis/api-pubsub @googleapis/yoshi-python
 
-# The python-samples-reviewers team is the default owner for samples changes
-/samples/   @googleapis/api-pubsub @googleapis/python-samples-owners
+# Additionally, the python-samples-reviewers team is also among the default owners for samples changes
+/samples/   @googleapis/api-pubsub @googleapis/python-samples-owners @googleapis/yoshi-python