message: docs: clarify the return type of file.data of uploadFile
diff: @@ -58,10 +58,10 @@ You can use the file key at the following place.
  #### Parameters
  | Name | Type | Required | Description |
  -| --------- | :-----: | :------: | -------------------------------------- |
  +| --------- | :--------------------------------------------------------------------------: | :------: | -------------------------------------- |
  | file | Object | Yes | An object includes file name and data. |
  | file.name | String | Yes | The name for the file. |
  -| file.data | unknown | Yes | The data for the file. |
  +| file.data | String or<br />[Blob](https://developer.mozilla.org/en-US/docs/Web/API/Blob) | Yes | The data for the file. |
  #### Returns
  