Create mandelbrot.py example

[AlexJMcIntyre]

Hel thought you might be interested in my example showing how to plot the Mandelbrot set fractal. It's colourful and doesn't need a lot of code but gets quite a striking visual (after a good long render time)

[Gadgetoid]

Nice! I wonder if @micropython.native would make the mandel function any faster. Though painting pixels in vertical columns is going to be painfully slow anyway.