Modernize Docker workflow, add support for AMD

[chancecardona]

This just fixes some docker issues I was running into on my machine. I also added some AMD support sections using pocl. Now we can just say docker compose build beignet docker compose run beignet. Then the workflow I do is to copy whatever I want into the local "build" repo and that shows up in the /coriander/build/out directory where I can then run cocl_py despite not using python 2 on my system at all.

I can see that a large usecase for this repo has already been filled by the ZLUDA or HIPIFY nowadays combined with HIP/ROCm, but outputting to OpenCL feels valuable on its own and afaik there's not another way to do this specific niche.

[hughperkins]

Thanks! Do you know you have renamed doc to docs? Any particular reason for that? Note that you will need to update the links for images, you can see there is at least one broken image link at https://github.com/chancecardona/coriander/tree/improved-docker .