Add Bouncy Bubbles p5.js demo

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I'm not thrilled about the hacky pytest workaround, but I don't know of a way to test purely graphical web pages...

There's a weird issue with all p5.js examples which use the

    <script>
      function setup() {}
    </script>

workaround, to wit: a number is printed in the browser window, above the sketch canvas.

It seems to be specifically related to using js.window.requestAnimationFrame(create_proxy(draw)) in the sketch, as it doesn't show up for "static" sketches (e.g. #14)

Signed-off-by: Ben Alkov ben.alkov@gmail.com