hilla: add example usage of EndpointExposed

articles/hilla/lit/guides/endpoints.adoc

@@ -54,6 +54,41 @@ include::{root}{root-fix}/src/main/java/com/vaadin/demo/fusion/accessingbackend/
 The only difference is that `@BrowserCallable` doesn't support the `value` attribute. This means the endpoint name is always the same as the class name.
 
 
+=== Extending Other Classes
+
+Endpoints are standard Java classes and can extend other classes and implement interfaces. However, to prevent unintentional exposure, methods inherited from superclasses aren't generated by default.
+
+To expose methods from a superclass, use the `@EndpointExposed` annotation.
+
+The following example demonstrates that only methods from the endpoint itself and annotated superclasses are generated. The same principle applies to interfaces.
+
+[source,java]
+----
+@EndpointExposed
+public class ExposedClass {
+    public String fromExposedClass() { // <1>
+        return "Hello from ExposedClass";
+    }
+}
+
+public class NonExposedClass extends ExposedClass {
+    public String fromNonExposedClass() { // <2>
+        return "Hello from NonExposedClass";
+    }
+}
+
+@Endpoint
+public class EndpointClass extends NonExposedClass {
+    public String fromEndpointClass() { // <3>
+        return "Hello from EndpointClass";
+    }
+}
+----
+<1> This method is generated in `EndpointClass`.
+<2> This method is not generated, as its class is not annotated.
+<3> This method is generated, as it's in the endpoint class.
+
+
 == Modules Generated from Hilla Endpoints
 
 Hilla generates a TypeScript module for every Hilla endpoint on the backend. Each such module exports all of the methods in the endpoint.