Support the arguments property of scenario steps in CucumberJS JSON

[delatrie]

CucumberJS emits step arguments in the following format:

{
  "arguments": [
    {
      "content": "Lorem Ipsum...",
      "line": 7
    }
  ]
}

{
  "arguments": [
    {
      "rows": [
        { "cells": ["a", "b"] },
        { "cells": ["1", "2"] },
        { "cells": ["3", "4"] }
      ]
    }
  ]
}

Which differs from how the reference implementation of the JSON formatter emits them.