p5js/3d-flying-camera - Fix bug on non-square canvases
p5js/3d-flying-camera - Fix bug on non-square canvases

* Silly bug, using width in calculation of the centerY value.
* Developed on a square canvas ... so didn't see this until deploying.

brianhonohan/sketchbook,brianhonohan/sketchbook,brianhonohan/sketchbook