Add diagram for JWT Validation

Author: darshils2001

articles/application-gateway/json-web-token-overview.md

@@ -29,6 +29,8 @@ By performing token validation at the edge, Application Gateway simplifies appli
 > [!NOTE]
 > Tokens must be issued by Microsoft Entra ID
 
+ :::image type="content" source="media/json-web-token-overview/jwt-validation.png" alt-text="JWT Validation Diagram for Application Gateway.":::
+
 ## Prerequisites
 
 - **Application Gateway Requirements**