That feature is not available anymore on Facebook so this extension is useless at the moment...
Facebook Photo Info
Facebook has a technology that can detect what there is in the image and add that information in the photo. That extension show that information in the photo description in the right.
That extension is inspired from https://github.com/ageitgey/show-facebook-computer-vision-tags.
The difference that this is very light and show only the content of the photo without any emoji.