Examine source code of Check It Out

{
  "name": "Check It Out",
  "short_name": "Check It Out",
  "description": "Used on eBay or Amazon, we'll remind you when you are not buying directly from the manufacturer or a retailer you know and trust.",
  "version": "1.6",
  "manifest_version": 2,
  "author": "Electrical Safety First",
  "permissions": [
    "*://www.electricalsafetyfirst.org.uk/*",
    "storage"
  ],
  "icons": {
    "16": "assets/images/app-icon-16.png",
    "48": "assets/images/app-icon-48.png",
    "128": "assets/images/app-icon-128.png"
  },
  "background": {
    "scripts": [
      "modules/background.js"
    ],
    "persistent": false
  },
  "page_action": {
    "default_icon": {
      "16": "assets/images/toolbar-icon-16.png",
      "24": "assets/images/toolbar-icon-24.png",
      "32": "assets/images/toolbar-icon-32.png"
    },
    "default_title": "Check It Out",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.amazon.co.uk/*"
      ],
      "js": [
        "firefox.js",
        "modules/popper.js",
        "modules/utils.js",
        "modules/amazon.js"
      ],
      "all_frames": true
    },
    {
      "matches": [
        "https://www.ebay.co.uk/*"
      ],
      "js": [
        "firefox.js",
        "modules/popper.js",
        "modules/utils.js",
        "modules/ebay.js"
      ],
      "all_frames": true
    }
  ],
  "homepage_url": "https://www.electricalsafetyfirst.org.uk/check-it-out/?ref=extension",
  "web_accessible_resources": [
    "assets/fonts/filson-pro-book.woff",
    "assets/fonts/filson-pro-book.woff2",
    "assets/fonts/filson-pro-bold.woff",
    "assets/fonts/filson-pro-bold.woff2",
    "assets/fonts/filson-pro-medium.woff",
    "assets/fonts/filson-pro-medium.woff2",
    "assets/images/icon-basket-white.svg",
    "assets/images/icon-cross-white.svg",
    "assets/images/icon-loader-white.svg",
    "assets/images/icon-logo-white.svg",
    "assets/styles/global.css",
    "assets/styles/amazon.css",
    "assets/styles/ebay.css",
    "components/banner.html",
    "components/tab.html",
    "components/popup--amazon.html",
    "components/popup--ebay.html"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "checkitout@thisisabsurd.com"
    }
  }
}