Slurm job array

[jen-reeve]

we should have some docs on this

[geoffreyweal]

Do we not already? Strange I thought we did. I learnt about arrays from nesi

[jen-reeve]

Ah we do, but the subpage didn't come up when I was searching!

[CallumWalley]

Yep, been meaning to split it into it's own page for a while.

[CallumWalley]

working on in #1023