Scale deployments using a dedicated CLI command

Streamline the process for scaling a deployment by a given number of replicas using the `scale` command

```
krane scale my-app --replicas 3
```

shorthand:

```
krane scale my-app -r 3
```

**Flags:**
- **--replicas** (-r)
required: `true`
type: `number` (should be a non-negative number)

Start by locating the CLI entry point and the existing deployment-related commands. Implement the `scale` command with the required `--replicas`/`-r` option and verify that non-negative numeric values are handled. Done means `krane scale my-app --replicas 3` and its shorthand invoke scaling successfully.

Written by the indexing model from the issue text.