Add Dark Mode / Night Mode as an inspector option

[kkoppenhaver]

This would essentially invert the colors: dark background, outlines of all the sprites white.

This might require generating a new sprite sheet just for this.

[kkoppenhaver]

Seems this already exists, just needs to be hooked up to an inspector control instead of happening on a timer.

https://github.com/alphaparticlecode/block-a-saurus/blob/master/src/js/Dino.js#L575