Circle packing example

[FayCarsons]

I thought it would be nice to have an example of more complex use of this library, so I threw together a quick circle packing example. It has a couple of issues I would love some input on fixing - namely typing, accessing the point and radius of a circle, and doing destructuring of circles in function args isn't possible without the type declaration in shape.mli which brings up other issues. But that's the temporary fix I went with.

The result:

I would have liked to fill each circle with concentric circles of changing colors using the repeat function or similar, but getting all the types to play nice was difficult and I feel like getting advice from someone more experienced with OCaml would be better than me wasting more time wrestling with type inference.

[FayCarsons]

Added concentric circles, the only glaring issue at this point (from my POV) is the typing issues and accessing circle fields.

Here's the current result:

[FayCarsons]

I refactored this to remove the typing issues, and labeled the colors in the palette. I still think there's probably a better way to do this, currently it doesn't really use the library for anything except rendering, but I'm not super sure what the solution is.