Add documentation on how to use ROCM on System76

[guilt]

For those with somewhat recent AMD graphics cards, they should be able to run ROCM via Docker easily.

I was asked to add this to the support docs, so I am going to start by adding this ticket here.

I have already added the basic steps/scripts in this gist but I am looking for more volunteers to test it. In the meantime, let me try to come up with better documentation that could be added to the portal. Even though I suck at it.