This is a quick and dirty PR whose aim is to show that supporting rst in scrapers is not that crazily difficult.

As it stands the breaking changes are:

• there is no single img behaviour.
• different scrapers images are on different lines (I would say this is a good thing although it just happened like this)

I checked that the galleries look similar. I haven't tried to implement a meaningful PNGImageScraper although I suspect that it would not be that different from the one in your PR doc. I think with the rst support you could also add the filename somewhere (e.g. in the figure caption)