20221121 / Documentation update

Some updates in our slurm documentation, see:

• https://meso-centres-lyon.pages.in2p3.fr/psmn-rtd/clusters_usage/submitting.html#slurm-commands (slurm basics)
• https://meso-centres-lyon.pages.in2p3.fr/psmn-rtd/clusters_usage/computing_resources.html#features (features/constraints)
• https://meso-centres-lyon.pages.in2p3.fr/psmn-rtd/clusters_usage/partitions_overview.html (features/constraints)