docs: fix typo (#849)

docs/4.examples/stream-response.md

@@ -12,7 +12,7 @@ Streaming is a powerful feature of h3. It allows you to send data to the client
 To stream a response, you first need to create a stream using the [`ReadableStream`](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream) API:
 
 ```ts
-const steam = new ReadableStream();
+const stream = new ReadableStream();
 ```
 
 For the example, we will create a start function that will send a random number every 100 milliseconds. After 1000 milliseconds, it will close the stream: