Please add an option to make placeholders visible Noté 4 sur 5 étoiles

Great addon.

But i miss an option to make the placeholders visible (border, different color, visible image).

Sometimes there are broken sites, where i am not sure, if wanted images are blocked, or if the site is broken and there is really nothing to see.

Cette critique est pour une version précédente du module (2.2.1.1-signed).