Tutorial on how to build pytorch 3d wheels

I would like to tackle the `build pytorch3d wheels` issue since the code in this repo is outdated and many people are asking for this feature. I created a repo [here](https://github.com/domef/pytorch3d-wheels) with a Dockerfile and some bash scripts that allow to build wheels for various version combinations of python/pytorch/pytorch3d/cuda.

I would like to integrate it in the main pytorch3d repo so that all people can easily use it. Let me know if this is welcome and if there are some guidelines/preferences on how to move the code here (probably the old code can be removed). I'll try to create a pull request as soon as possible in my spare time.