Examine source code of Workona New Tab

{
  "manifest_version": 2,
  "name": "Workona New Tab",
  "short_name": "Workona New Tab",
  "version": "1.0.2",
  "minimum_chrome_version": "54",
  "description": "Add Workona to your Firefox new tab.",
  "homepage_url": "https://workona.com",
  "icons": {
    "16": "images/icon_16.png",
    "32": "images/icon_32.png",
    "48": "images/icon_48.png",
    "96": "images/icon_96.png",
    "128": "images/icon_128.png",
    "256": "images/icon_256.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "firefox-prod-newtab@firefox-workona.com"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "https://workona.com/*"
      ],
      "js": [
        "messagePassing.js"
      ],
      "run_at": "document_start"
    }
  ]
}