[DO] Get started to mention how to add to existing Worker (cloudflare#24552)

* Adding a note component to address adding DO to existing Worker

* Adding required code block

* Using bullets instead of numbers

* Updating comment

Author: Oxyjun

src/content/docs/durable-objects/get-started.mdx

@@ -62,6 +62,39 @@ Move into your new directory:
 cd durable-object-starter
 ```
 
+:::note[Adding a Durable Object to an existing Worker]
+
+To add a Durable Object to an existing Worker, you need to:
+
+- Modify the code of the existing Worker to include the following:
+
+  ```ts
+  export class MyDurableObject extends DurableObject<Env> {
+    constructor(ctx: DurableObjectState, env: Env) {
+      // Required, as we're extending the base class.
+      super(ctx, env)
+    }
+
+    {/* Define your Durable Object methods here */}
+
+  }
+
+  export default {
+    async fetch(request, env, ctx): Promise<Response> {
+      const id:DurableObjectId = env.MY_DURABLE_OBJECT.idFromName(new URL(request.url).pathname);
+
+      const stub = env.MY_DURABLE_OBJECT.get(id);
+
+      {/* Access your Durable Object methods here */}
+
+    },
+  } satisfies ExportedHandler<Env>;
+  ```
+
+- Update the Wrangler configuration file of your existing Worker to bind the Durable Object to the Worker.
+
+:::
+
 ## 2. Write a Durable Object class using SQL API
 
 Before you create and access a Durable Object, its behavior must be defined by an ordinary exported JavaScript class.