Examine source code of Picture Frame Mode

{
  "manifest_version": 2,
  "name": "Picture Frame Mode",
  "version": "1.0",
  "description": "Places decorative frames around images on web pages (wood, gold, modern, minimal).",
  "permissions": [
    "storage",
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{bb690783-f7f1-4708-9b03-c26d494357ea}"
    }
  }
}