Add dockerRunOptions setting

[jacobtomlinson]

Closes #63

Enables you to specify docker specific run flags to enable more flexible usage with dockerRunOptions.

apiVersion: container-canary.nvidia.com/v1
kind: Validator
name: gpu
description: A GPU example to show you can pass extra flags to Docker
command:
- "sleep"
- "30"
dockerRunOptions:
- "--gpus"
- "all"
checks:
  - name: nvidia-smi
    description: 📦 Can run nvidia-smi
    probe:
      exec:
        command:
          - /usr/bin/nvidia-smi
      initialDelaySeconds: 1