Tab-autocomplete `ruff config`

Would be great if `ruff config` tab autocompletes:

```
ruff config is
# tab
ruff config isort
```

and

```
ruff config isort.spl
# tab
ruff config isort.split-on-trailing-comma
```

Related: https://github.com/charliermarsh/ruff/issues/2808 hence pinging @not-my-profile 