Update README.md

README.md

 
 When download complete, DownloadManager will generate a file path so that you can deal with it.
 
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 ```js
 RNFetchBlob
     .config({
     })
 ```
 
+Your app might not have right to remove/change the file created by Download Manager, therefore you might need to [set custom location to the download task](https://github.com/wkh237/react-native-fetch-blob/issues/236).
 
 **Download Notification and Visibility in Download App (Android Only)**