[Challenge] Sandpile Fractals on p5.js

Also known as Abelian sandpile models, these fractals are really cool looking and have a fairly simple computation algorithm. Here's a [link](https://en.wikipedia.org/wiki/Abelian_sandpile_model) to the Wikipedia page. Here's a [video](https://youtu.be/1MtEUErz7Gg) by numberphile explaining this concept.

No source file, test, or entry point is named. Read the linked Wikipedia article and Numberphile video first; the issue does not define an acceptance condition beyond exploring an Abelian sandpile fractal in p5.js, so the expected completed work needs clarification.

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