Hi-Vis Suspicious blocks

This is just a basic retexture of the suspicious sand and gravel, made from minor edits to the vanilla textures, meant to increase contrast and make it easier to tell the normal blocks from the suspicious ones.

I had a friend who had great difficulty discerning the suspicious gravel and sand, and I was dissatisfied with many of the visibility mods as they tended to be a bit jarring and immersion breaking. So I just made my own, it's not perfect but I think that it is an improvement over vanilla as well as some other offerings.