Examine source code of Smart SEO Highlighter

{
  "manifest_version": 2,
  "name": "Smart SEO Highlighter",
  "version": "8.4.2",
  "description": "Best SEO Firefox Add-on: Highlights headings, nofollow links, checks content quality, shows mobile view, and checks SEO issues.",
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/h1-heading.png",
      "48": "icons/h1-heading.png"
    }
  },
  "permissions": [
    "storage",
    "activeTab",
    "webRequest",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "icons/h1-heading.png",
    "48": "icons/h1-heading.png",
    "128": "icons/h1-heading.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "web_accessible_resources": [
    "highlight.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "smart-seo-highlighter@example.com"
    }
  }
}