New example for drawing arcs and circle sections

[joffreybesos]

There is no draw.arc() function and it seems the lyon crate only supports it for SVGs.
I had a use case that required this, so I've come up with a helper function that essentially achieves the same thing by drawing a path.
I've written it as an example in case it comes in handy for someone else, since dealing with the math is a pain.

[Nazariglez]

Thank you so much! this looks great!