Link to dnssec-for-secondary from the setup page

Author: RebeccaTamachiro

src/content/docs/dns/zone-setups/zone-transfers/cloudflare-as-secondary/setup.mdx

@@ -19,6 +19,7 @@ With [incoming zone transfers](/dns/zone-setups/zone-transfers/cloudflare-as-sec
 ## Before you begin
 
 - You should already have a registered domain, set up with your primary DNS provider.
+- Review the available options and plan for how you will use [DNSSEC with Cloudflare as secondary](/dns/zone-setups/zone-transfers/cloudflare-as-secondary/dnssec-for-secondary/).
 - Make sure you have completed the following tasks at your primary DNS provider and at Cloudflare.
 
 ### At your primary DNS provider