Examine source code of PageTrek

{
  "manifest_version": 2,
  "name": "PageTrek",
  "version": "1.0",
  "description": "Highlights dead links in a page.",
  "icons": {
    "48": "icons/pagetrek-48.png"
  },
  "permissions": [
    "activeTab",
    "webRequest",
    "<all_urls>",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_scripts/extraction.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icons/pagetrek-32.png",
    "default_title": "PageTrek",
    "default_popup": "popup/start_trek.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "75.0"
    }
  }
}