title: JSON Schema Compare two properties to be equal length array
body: <p>I have two properties in a schema which are both arrays. I would like to compare that they're equal length.</p>
  
  <p>For example:</p>
  
  <h1>schema.json</h1>
  
  <pre><code>{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "type": "object",
    "properties": {
      "thing": {
        "type": "object",
        "properties": {
          "fields": {
            "type": "array",
            "items": {}
          },
          "values": {
            "type": "array",
            "items": {}
          }
        },
        "required": ["fields", "values"]
      }
    }
  }
  </code></pre>
  
  <h1>data.json</h1>
  
  <pre><code>{
    "thing": {
      "fields:": ["age", "sex", "location"],
      "values:": [25, "Male", "Cape Town"]
    }
  }
  </code></pre>
  
  <p>What I would like is to compare that fields and values are the same length in the schema. How would I do that?</p>