Display current image/video folder name

[jeylau]

We could set it as the layer name (though we should be careful as metadata['name'] is used in the h5 writer.

[VAmoroso13]

This would be a great addition as I currently don't see an option to show what photo file you're working on. After running deeplabcut.check_labels() and reviewing, it would make it easier to map the problematic image to that which needs to be corrected in Napari; especially when the number of images is in the thousands.

Thanks!