DISCO-000 add call to action (#22297)

* DISCO-000 add call to action

* Update src/content/docs/google-tag-gateway/index.mdx

Co-authored-by: Ruskin <[email protected]>

* Update src/content/docs/google-tag-gateway/index.mdx

Co-authored-by: Ruskin <[email protected]>

---------

Co-authored-by: Ruskin <[email protected]>

Author: 2 people

src/content/docs/google-tag-gateway/index.mdx

@@ -8,7 +8,7 @@ sidebar:
 
 ## Get started
 
-Google tag gateway for advertisers allows website owners using Cloudflare as a CDN to get the most out of ad measurement tools with just a few clicks.
+Google tag gateway for advertisers allows website owners using Cloudflare as a CDN to get the most out of ad measurement tools with just a few clicks. Note: setting this up [directly in Google Tag Manager](https://support.google.com/analytics/answer/16061641) is the fastest way to use this feature.
 
 ### Configure Google tag gateway for advertisers in the dashboard