doc: add documentation for blob.bytes() method

doc/api/buffer.md

@@ -538,6 +538,17 @@ added:
 Creates and returns a new `Blob` containing a subset of this `Blob` objects
 data. The original `Blob` is not altered.
 
+#### `blob.bytes()`
+
+The `blob.bytes()` method returns the byte of the `Blob` object as a `Promise<Uint8Array>`.
+
+```js
+const blob = new Blob(['hello']);
+blob.bytes().then((bytes) => {
+  console.log(bytes); // Outputs: Uint8Array(5) [ 104, 101, 108, 108, 111 ]
+});
+```
+
 ### `blob.stream()`
 
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