added example to keyCode and refactored keyPress example
added example to keyCode and refactored keyPress example

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