buffer: add JSDoc to blob bytes method

PR-URL: https://github.com/nodejs/node/pull/54117
Reviewed-By: Jake Yuesong Li <jake.yuesong@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

lib/internal/blob.js

@@ -312,6 +312,9 @@ class Blob {
     return dec.decode(await this.arrayBuffer());
   }
 
+  /**
+   * @returns {Promise<Uint8Array>}
+   */
   bytes() {
     if (!isBlob(this))
       throw new ERR_INVALID_THIS('Blob');