[Feature] Add support for showing thumbnail in default FilePicker experience on Uno platforms #2
Description
Describe the feature and how it will be used
While porting over the FilePicker to support Uno platforms, it was noted that the StorageFile.GetThumbnailAsync method is not supported. This led to the control visually being ported across and supported but the base UI isn't the same across platforms.
Once unoplatform/uno#5637 is complete, this work can be started and finished off.