[Opensource contributions] 2D-to-3D color mapping

[layumi]

Hi @akanazawa
Thanks a lot for the great code.
I add the 2D-to-3D color mapping function in the final obj file at https://github.com/layumi/hmr.
It would be great if you can consider to include the link in the [Opensource contributions].
I hope it may help other beginners in the community. Thanks a lot~~

[akanazawa]

Cool!! updated, thanks :)!