title: React Native Download image from url and save in Gallery
body: <p>I want download image from URL and save in the Gallery.</p>
  
  <p>This source works well on Android, but not iOS.</p>
  
  <pre><code>import RNFetchBlob from "rn-fetch-blob";
  
  
  let imgUrl = 'https://static.scientificamerican.com/sciam/cache/file/EAF12335-B807-4021-9AC95BBA8BEE7C8D_source.jpg'
  
  let newImgUri = imgUrl.lastIndexOf('/');
  let imageName = imgUrl.substring(newImgUri);
  
  let dirs = RNFetchBlob.fs.dirs;
  let path = Platform.OS === 'ios' ? dirs['MainBundleDir'] + imageName : dirs.PictureDir + imageName;
  
   RNFetchBlob.config({
       fileCache: true,
       appendExt: 'png',
       indicator: true,
       IOSBackgroundTask: true,
       path: path,
       addAndroidDownloads: {
           useDownloadManager: true,
           notification: true,
           path: path,
           description: 'Image'
        },
  
       }).fetch("GET", imgUrl).then(res =&gt; { 
              console.log(res, 'end downloaded') 
     });
  </code></pre>
  
  <p>witch one Permissions I needs for iOS, to save Photo in the Gallery? </p>