Quiet mode option

When running Link 'unsupervised', e.g. when using `LOAD=∘∘∘`, it would be nice if there was a way to silence Link's diagnostic output:

```text
Link Warning: ⎕SE.Link.Create: .NET or .NetCore not available - watch defaults to 'ns'
Linked: # → /src
```

Maybe we could have a

```apl
]link.create # /my/path/here --quiet
```

(although I prefer commands be quiet by default, and instead have a --verbose option).

This would be nice when running APL code in Docker, in GitHub actions etc, not to have Link 'pollute' the output.