Add amd64nvidia image for Nvidia HwAccel ffmpeg

[huyqt]

• Added Dockerfile.ffmpeg.amd64nvidia to build ffmpeg with Nvidia hardware accelerated capabilities.
  • Based on blakeblackshear/frigate-ffmpeg:amd64nvidia which is based on jrottenberg/ffmpeg.
• Added Dockerfile.amd64nvidia to include the ffmpeg that was built and build the necessary base environment to operation within.
  • Based on blakeblackshear/frigate:amd64nvidia which is based on https://gitlab.com/nvidia/container-images/cuda/-/blob/master/dist/11.1.1/ubuntu1804/base/Dockerfile on top of the existing Dockerfile.ubuntu.

If pulled, the XML needs to be updated to reflect oznu repository.

[oznu]

Thanks for the effort put into this; I think this is beyond the scope of the project and what I'm willing to support going forward. You are more than welcome to maintain a parallel branch with this build for others that might find it useful 😄