Add rounded corners

[isaacvr]

Now the puzzle have a better user interface by adding some roundness to the corners.

[mfeather1]

Thank you for your contribution showing how to implement rounded corners with bezier curve, we are reviewing it.

[bcube2]

Thank you for your pull request. There are some issues with your submitted code, such as:

1. it seems to be not working correctly with the hint and supercube parameters
2. there is no option to specify which corners get rounded

As it turned out, these can be fixed. We do think it is a nice and elegant enhancement, so we added it to the Enhancement section of the AnimCubeJS documentation page (check it out here with a simplified code).

If there is a convenient programming way (which I don´t see) for adjusting roundness and specifying which corners get rounded by non-programmers via parameters (default being no roundness for all corners), I would certainly support implementing it to all 2x2x2 - 7x7x7 programs.