chore: add CODEOWNERS and repo sync (#127)

Author: JustinBeckwith

packages/proto-plus/.github/CODEOWNERS

@@ -0,0 +1,7 @@
+# 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
+
+* @googleapis/actools @googleapis/yoshi-python

packages/proto-plus/.github/sync-repo-settings.yaml

@@ -0,0 +1,26 @@
+rebaseMergeAllowed: false
+squashMergeAllowed: true
+mergeCommitAllowed: false
+branchProtectionRules:
+- pattern: master
+  isAdminEnforced: true
+  requiredStatusCheckContexts:
+    - 'ci/circleci: docs'
+    - 'ci/circleci: style-check'
+    - 'ci/circleci: unit-3.5'
+    - 'ci/circleci: unit-3.6'
+    - 'ci/circleci: unit-3.7'
+    - 'ci/circleci: unit-3.8'
+    - 'ci/circleci: unit-cpp-3.5'
+    - 'ci/circleci: unit-cpp-3.6'
+    - 'ci/circleci: unit-cpp-3.7'
+    - 'ci/circleci: unit-cpp-3.8'
+    - 'cla/google'
+  requiredApprovingReviewCount: 1
+  requiresCodeOwnerReviews: true
+  requiresStrictStatusChecks: true
+permissionRules:
+  - team: yoshi-python
+    permission: push
+  - team: actools
+    permission: admin