chore: require samples checks (#101)

Make samples kokoro sessions required

Author: busunkim96

packages/google-cloud-bigquery-storage/.github/sync-repo-settings.yaml

@@ -0,0 +1,13 @@
+# https://github.com/googleapis/repo-automation-bots/tree/master/packages/sync-repo-settings
+# Rules for master branch protection
+branchProtectionRules:
+# Identifies the protection rule pattern. Name of the branch to be protected.
+# Defaults to `master`
+- pattern: master
+  requiredStatusCheckContexts:
+    - 'Kokoro'
+    - 'cla/google'
+    - 'Samples - Lint'
+    - 'Samples - Python 3.6'
+    - 'Samples - Python 3.7'
+    - 'Samples - Python 3.8'