Add information about circle entity secret

Author: d4mr

apps/portal/src/app/engine/features/wallet-credentials/page.mdx

@@ -42,6 +42,13 @@ Credentials are created in the dashboard and can be reused across multiple walle
 5. Populate the credential fields which are specific to the type.
 6. Click on **Create**.
 
+<Details id="circle" summary="Circle Credentials">
+	Circle credentials require an `entitySecret` to be created and registered
+	before creating a credential with engine. Consult
+	https://developers.circle.com/w3s/entity-secret-management to create and
+	register an entity secret.
+</Details>
+
 ## Usage
 
 When creating a wallet, you can either: