Add the API proxy address for EU workspaces

We only mention "api.segment.io" which is used for regular workspaces. EU workspaces would use a different domain: "events.eu1.segmentapis.com"

Author: prigiattiperrut

src/connections/sources/catalog/libraries/website/javascript/custom-proxy.md

@@ -23,9 +23,13 @@ This guide explains how to set up a custom domain in CloudFront. You can apply t
 You need to set up two important parts, regardless of the CDN provider you use:
 
 - Proxy to Segment CDN (`cdn.segment.com`)
-- Proxy to Segment tracking API (`api.segment.io`)
+- Proxy to Segment tracking API (`api.segment.io`). If you are using a [Regional Workspace](/docs/guides/regional-segment/#client-side-sources), please note that instead of using `api.segment.io` to proxy the Tracking API, you'll be using `events.eu1.segmentapis.com`
+
+
 
 > info " "
+> If you are using a [Regional Workspace](/docs/guides/regional-segment/#client-side-sources), please note that instead of using `api.segment.io` to proxy the Tracking API, you'll be using `events.eu1.segmentapis.com`
+> 
 > Segment only has the ability to enable the proxy setting for the Web (Analytics.js) source. Details for mobile source proxies are in the [Analytics for iOS](/docs/connections/sources/catalog/libraries/mobile/ios/#proxy-https-calls) and [Analytics for Android](/docs/connections/sources/catalog/libraries/mobile/android/#proxying-http-calls) documentation.  It is not currently possible to set up a proxy for server sources using the Segment UI.
 
 ## Set up