docs: render.js preload fix
docs: render.js preload fix

same as https://github.com/processing/p5.js-website/pull/524

dhowe/p5.js,limzykenneth/p5.js,processing/p5.js,dhowe/p5.js,mlarghydracept/p5.js,processing/p5.js,limzykenneth/p5.js,mlarghydracept/p5.js