added fold definitions and choice button controls

finalised the layout made the boxes the paper airplane can be shaped and can be slingshotted into the simlator, made its skeletons also i initially wanted to make the paper airplane foldable by hand but turns out its way out of my skillset after talking to claude for a while so i lowk js gave up i made it changeable via buttons tho ╰(°▽°)╯

even tho its not shipped and all, anyone can check it out at: https://samirghimire.me/paper-sim/

the url is also there in the pictures, cheers :)