Add description for new GPUs

[GanZhang-GFD]

Keeling recently added a few GPUs. These GPUs passed initial verification tests and can be utilized by authorized users. It would be great to add a section to describe how to access the new resource.

Here is sample batch script provided by Ken:

#! /bin/bash

#SBATCH -p l40s
#SBATCH -N 1
#SBATCH -n 96
#SBATCH --gres=gpu:L40S:1
#SBATCH --constraint=tl40s
#SBATCH --mem=250000
#SBATCH --time=48:00:00
#SBATCH --output=batchout

module purge
module load gnu/gnu-6.1.0
module load L40S

time ./histogram 

Interactive batch jobs have also been tested. Users just need to replace standard parameter values with the GPU-specific ones (e.g., partition, gres, etc.)