Add flow of job allocation

Add an overview over job allocation similar to the following diagram, perhaps using mermaid (see also its integration page or directly the corresponding plugin page):

sequenceDiagram
    user ->>+ login node: run programm
    login node ->> login node: kill after 5 min
    login node ->>- user: Killed!
    user ->> login node: salloc [...]
    login node ->> Slurm: Request resources
    Slurm ->> user: resources
    user ->>+ allocated resources: srun [options] [command]
    allocated resources ->> allocated resources: run command (on allocated nodes)
    allocated resources ->>- user: program finished
    user ->>+ allocated resources: srun [options] [further_command]
    allocated resources ->> allocated resources: run further command
    allocated resources ->>- user: program finished
    user ->>+ allocated resources: srun [options] [further_command]
    allocated resources ->> allocated resources: run further command
    Slurm ->> allocated resources: Job limit reached/exceeded
    allocated resources ->>- user: Job limit reached