Please support `roundRect`

[shamansir]

https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/roundRect

This shape isn't trivial to implement with paths, unfortunately.

[joakin]

Sounds good and should be fairly easy to support. Would you like to try a pull request?

[fgerodez]

Hi,

I made a PR to add the method to the elm api : https://github.com/joakin/elm-canvas/pull/41/files

If you can tell me what you think :)