Adding log driver opts

[JoeColeman95]

Adding logging driver and logging options availability to the plugin.
This allows passing of custom log-driver and log-opt

For example:

steps:
  - label: "Hello World"
    command: "echo 'Hello, world'"
    plugins:
      - docker#v5.13.0:
          image: "alpine:latest"
          log-driver: "json-file"
          log-opt:
            - "max-size=1m"
            - "max-file=2"

This Fixes: #284

Also updates README.md to reflect changes and adds new unit tests.