docs(samples): add codeowner file (#180)

Author: stephaniewang526

.github/CODEOWNERS

@@ -0,0 +1,8 @@
+# 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
+
+# The java-samples-reviewers team is the default owner for samples changes
+samples/**/*.java                        @stephaniewang526 @googleapis/java-samples-reviewers