doc: add documentation for blob.bytes() method

Author: jmsb02

doc/api/buffer.md

@@ -540,12 +540,14 @@ data. The original `Blob` is not altered.
 
 #### `blob.bytes()`
 
-The `blob.bytes()` method returns the byte of the `Blob` object as a `Buffer`.
+The `blob.bytes()` method returns the byte of the `Blob` object as a `Promise<Uint8Array>`.
 
 ```js
 const blob = new Blob(['hello']);
-console.log(blob.bytes()); // Outputs: <Buffer 68 65 6c 6c 6f>
-
+blob.bytes().then((bytes) => {
+  console.log(bytes); // Outputs: Uint8Array(5) [ 104, 101, 108, 108, 111 ]
+});
+```
 
 ### `blob.stream()`