Add docs example with p5.SVG

[tonyketcham]

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Pen plotters + p5 + Svelte would be a great example that some may find inspiring. That was one of the founding pieces of inspiration for starting this project and I was disappointed that p5.SVG didn't support ESM/instance mode so I couldn't get an SVG runtime for p5 working w/ p5-svelte.

In a recent release, p5.SVG added support for those pieces 🥳

[tonyketcham]

Turns out that the instance mode does the thing where it's trying to mod p5 via accessing the window which Svelte no likey. This may not work or may need a custom shim within p5-svelte in order to support

Experimenting with this on https://github.com/tonyketcham/p5-svelte-svg