Update Cloudflare docs with instructions for adding firewall rules

[zackkrida]

Problem

Our documentation about traffic anomalies is good, but doesn't specifically instruct on how to add Cloudflare firewall rules in our infrastructure repository.

Description

Add specific instructions for managing firewall rules in Terraform to the documentation site.

https://docs.openverse.org/meta/monitoring/traffic/runbooks/identifying-and-blocking-traffic-anomalies.html

Alternatives

Additional context