Apply rust in Gimp to improve the texture of rusty-truck

Texture to improve: http://magicalhex.com/textures/rusty-truck.png

See tutorial http://www.geocities.jp/gimproject3/gug-tutorials/textures/scott-effect.html

Open the rusty-truck texture at http://magicalhex.com/textures/rusty-truck.png and read the linked GIMP tutorial first. Locate where this texture is used in the game, apply the requested rust treatment in GIMP, and check the result in the browser game; done means the truck texture visibly has the intended rusty appearance.

Written by the indexing model from the issue text.