Add additional info for worker service binding rpc example (#20882)

* Add additional info for worker service binding rpc example

* Update src/content/docs/workers/runtime-apis/bindings/service-bindings/index.mdx

* Update src/content/docs/workers/runtime-apis/bindings/service-bindings/index.mdx

Author: ToriLindsay

src/content/docs/workers/runtime-apis/bindings/service-bindings/index.mdx

@@ -56,10 +56,10 @@ Worker A that declares a Service binding to Worker B can call Worker B in two di
 
 ## Example — build your first Service binding using RPC
 
+This example [extends the `WorkerEntrypoint` class](/workers/runtime-apis/bindings/service-bindings/rpc/#the-workerentrypoint-class) to support RPC-based Service bindings.
 First, create the Worker that you want to communicate with. Let's call this "Worker B". Worker B exposes the public method, `add(a, b)`:
 
 
-
 <WranglerConfig>
 
 ```toml