game.js documentation

[aquisenberry]

I don't know how/ if you want me to document game.js

[ericlathrop]

The Game class does need to be documented, and it would be awesome if you wanted to help.

The documentation system Splat uses is called JSDoc, and it's documentation is here: http://usejsdoc.org/

An example of what a documented class looks like is here:
https://github.com/SplatJS/splat-ecs/blob/master/lib/sound-loader.js

You don't really need to document the private functions, only what's on Game.prototype and Game itself. You should just mark makeScenes, makeScene, makeSceneData, installSystems, and onCanvasResize as @private so they don't show up in the docs.

If you run npm run build, the docs will be output into the docs folder, and you can open them in a web browser to make sure they look right.