devtools: add script for Cloud Armor

Add a script that displays our Cloud Armor policies and explains
how to change them.

Change-Id: I1e662bd91f886ae25288d114de120917c92ec40b
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/659896
LUCI-TryBot-Result: Go LUCI <[email protected]>
kokoro-CI: kokoro <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: jba

devtools/describe_cloud_armor.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+# Display the state of the Cloud Armor rules for the prod frontend.
+
+echo 'Cloud Armor rule for prod. Note rateLimitOptions.'
+
+gcloud compute security-policies describe prod-frontend
+
+echo
+echo 'To modify:'
+echo '- Obtain the necessary permissions.'
+echo '- Visit https://console.google.com/net-security/securitypolicies/details/prod-frontend?project=$PROJECT&hl=en&tab=rules'
+echo '- Click Edit'