Document deploying RAPIDS with SLURM

[jacobtomlinson]

We have existing SLURM documentation here https://rapids.ai/hpc. We should migrate this to the deployment documentation here.

Create a new documentation page called source/hpc/slurm.md with instructions on launching a Dask cluster with GPUs on a SLURM scheduler with dask-jobqueue and/or dask-mpi.

[jacobtomlinson]

This gist is a good starting point https://gist.github.com/jacobtomlinson/d101991adefc1e85e3dafd67ff7f1fb1