TF-3454 Download all attachments as ZIP

core/lib/domain/preview/supported_preview_file_types.dart

@@ -31,6 +31,7 @@ class SupportedPreviewFileTypes {
     'application/vnd.ms-powerpoint'];
 
   static const zipMimeTypes = [
+    'application/zip',
     'application/x-tar',
     'application/x-gtar',
     'application/x-gzip',

core/lib/presentation/resources/image_paths.dart

@@ -222,6 +222,7 @@ class ImagePaths {
   String get icDeleteSelection => _getImagePath('ic_delete_selection.svg');
   String get icLogoTwakeWelcome => _getImagePath('ic_logo_twake_welcome.svg');
   String get icHelp => _getImagePath('ic_help.svg');
+  String get icDownloadAll => _getImagePath('ic_download_all.svg');
 
   String _getImagePath(String imageName) {
     return AssetsPaths.images + imageName;