Reintroduce Sunset biome

[BlackYps]

Brings back the sunset biome. Visually it looks the same, just some internal values had to be tweaked as the shader now expects slightly different inputs. I included the height and roughness textures as separate images instead of the png of them all blobbed together. The idea was to provide the source images for easier edits, should someone want to tweak the biome in the future. But when they are already compiled to one big texture, then editing is not really practical. As an additional benefit, the memory footprint of the included images shrunk by ~11 MB.