Diagram suggestion for HPC use case content

[justinegeffen]

```
┌──────────────────┐                     ┌──────────────────────┐
│                  │                     │                      │
│ Seqera Platform  │ ◄──── outbound ──── │  Login node          │
│ (cloud or        │      secure         │  ┌────────────────┐  │
│  enterprise)     │     channel         │  │   tw-agent     │  │
│                  │                     │  └────────────────┘  │
└──────────────────┘                     │           │          │
                                         │           │ submits  │
                                         │           ▼          │
                                         │  ┌────────────────┐  │
                                         │  │ Slurm / LSF /  │  │
                                         │  │ PBS / SGE      │  │
                                         │  └────────────────┘  │
                                         │           │          │
                                         │           ▼          │
                                         │     Worker nodes     │
                                         └──────────────────────┘
```

I'm not a fan of diagrams like this. Can we describe it or make it a mermaid? Mermaid is installed in the docs repo now.

Originally posted by @christopher-hakkaart in #1618 (comment)