Add callout for IP

Author: maxvp

src/content/docs/cloudflare-one/connections/connect-devices/agentless/pac-files.mdx

@@ -300,6 +300,8 @@ Using your proxy endpoint's domain, you can get the IP addresses assigned to the
 
 </Tabs>
 
+For additional security, you can allowlist the static Cloudflare IPv4 address for proxy endpoints, `162.159.193.21`.
+
 ## Limitations
 
 ### Traffic limitations