NanoVG Haskell bindings

Currently only the GL3 backend is supported.

A large part of the example bundled with NanoVG is translated into Haskell and bundled as example00.

Most of the bindings directly expose the corresponding NanoVG so look there for more details on the usage.

There is also a diagrams backend using these bindings.

Feel free to open issues if you have any ideas for improvements (or even better PRs :)).