Usage of volumes

```yaml
# Volume test
envs:
  ENV1: "xxx"
  ENV2: "yyy"
docker: "ubuntu:18.04"
steps:
  - name: "List volumes at top level"
    description: "Descrição do passo"
    volumes:
      -
        source: /tmp/
        destination: /microci_workspace/tmp
        mode: rw
    plugin:
      name: bash
      bash: |
        ls /microci_workspace/tmp
```