Examine source code of Scroll Distance Tracker

{
  "manifest_version": 2,
  "name": "Scroll Distance Tracker",
  "version": "1.0",
  "description": "Track the distance a user scrolls on each webpage. The extension displays a small indicator showing the number of pixels or percentage scrolled, useful for reading long articles.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e8b7157d-93bc-4af2-aa1e-a8faf9740eed}"
    }
  }
}