title: Alexa APL Pager component not responding to OnPageChange event
body: <p>I've created a new APL (Alexa Presentation Language) template using the Pager component and attached a "OnPageChange" event listener. I want this event to call another Command however it is never being invoked.</p>
  
  <p>Reference to OnPageChange event mentioned in the docs here:
  <a href="https://developer.amazon.com/docs/alexa-presentation-language/apl-standard-commands.html#setpage-command" rel="nofollow noreferrer">https://developer.amazon.com/docs/alexa-presentation-language/apl-standard-commands.html#setpage-command</a></p>
  
  <p>I have tried invoking a simple SendEvent to listen if the event is ever fired.</p>
  
  <pre><code>{
    "parameters": ["payload"],
    "items": [
      {
        "type": "Container",
        "item": [
          {
            "id": "pagerCanvas",
            "type": "Pager",
            "width": "100vw",
            "height": "70vh",
            "data": "${payload.pagerData.items}",
            "navigation": "wrap",
            "onPageChanged": {
              "type": "Parallel",
              "delay": 0,
              "commands": [
                {
                  "type": "SendEvent",
                  "arguments": ["${event.source.value}"]
                }
              ]
            },
            "items": [
              {
                "type": "Image",
                "width": "100vw",
                "height": "100vh",
                "source": "${data.url}",
                "scale": "cover"
              }
            ]
          }
        ]
      }
    ]
  }
  </code></pre>
  
  <p>I expect a hit to my endpoint but receive nothing instead.</p>