via https://forums.tumult.com/t/impression-pixels-and-google-campaign-manager/16499/3?u=daniel

manifest.json

{
  "name": "PixelLoader",
  "type": "ci-studio-pixelloader",
  "tagName": "ci-studio-pixelloader",
  "version": 2,
  "description": "Easy loading of tracking pixels from creatives.",
  "defaultWidth": 25,
  "defaultHeight": 25,
  "isFixedSize": true,
  "externalScripts": [
    "https://www.gstatic.com/ads/ci/studio/pixelloader/1/pixelloader_min.js"
  ],
  "dependencies": [
    "gwd-doubleclick"
  ],
  "attributes": [
    {
      "name": "url",
      "label": "URL",
      "type": "string",
      "required": true,
      "description": "Url of the pixel to load."
    },
    {
      "name": "eventtype",
      "label": "Event type",
      "type": "string",
      "required": false,
      "description": "EventType pixelloader listens to.",
      "defaultValue": "manual"
    },
    {
      "name": "eventtarget",
      "label": "Event target",
      "type": "string",
      "required": true,
      "description": "EventTarget pixelloader monitors.",
      "defaultValue": "enabler"
    },
    {
      "name": "cumulative",
      "label": "Cumulative loading",
      "type" : "boolean",
      "required": false,
      "defaultValue": false,
      "description": "True if a pixel is loaded cumulative."
    }
  ],
  "methods": [
    {
      "name": "load",
      "label": "Load pixel",
      "description": "Triggers the pixel to load."
    }
  ],
  "events": [
    {
      "name": "load",
      "label": "Load",
      "description": "A pixel was loaded."
    }
  ],
  "nestable": false
}