Provide Sprite Graphics in Different Sizes, Depending on Viewport Width

[pahund]

If the viewport is small, use smaller images for the sprites, so that the animals are not significantly bigger than the gray boxes.

If the viewport is huge, provide bigger images.

[pahund]

Pixi v3 provides better scaling and anti-aliasing, so it may not be neccessary to have multiple images, we can just cale them down