little note on cross product offers (#945)

Author: vegaro

docs/tools/customer-center/customer-center-promo-offers-apple.mdx

@@ -19,6 +19,8 @@ This setup enables RevenueCat to automatically match the right offer based on a
 
 The SDK will automatically match the right offer based on a user’s actions and its active subscription. If the SDK cannot locate a matching promotional offer id for the currently active user's subscription, it will bypass the survey and proceed with the user’s requested action—either canceling or refunding the subscription.
 
+You can configure a promotional offer from either the same product as the user’s active subscription or from a different product within the same subscription group. For example, you can offer a discounted annual product to a user who is currently subscribed to a monthly product within the same subscription group.
+
 **These promotional offers must be created in App Store Connect in order to be shown to customers**
 
 ## Setting up promotional offers

docs/tools/customer-center/customer-center-promo-offers-google.mdx

@@ -17,6 +17,8 @@ This setup enables RevenueCat to automatically match the right offer based on a
 
 The SDK will automatically match the right offer based on a user's actions and its active subscription. If the SDK cannot locate a matching promotional offer id for the currently active user's subscription, it will bypass the survey and proceed with the user's requested action—either canceling or refunding the subscription.
 
+Google Play promotional offers can be applied to the same base plan the user is currently subscribed to, or to a different base plan within the same subscription. For example, you can offer a discounted annual plan to a user who is currently subscribed to a monthly plan.
+
 **These promotional offers must be created in App Store Connect and Google Play Store in order to be shown to customers**
 
 ## Setting up promotional offers