Examine source code of DjVu Reader

{
  "manifest_version": 2,
  "name": "DjVu Reader",
  "version": "1.0",
  "description": "View DjVu files directly in your browser.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "storage",
    "<all_urls>"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{64b8c596-dca3-4f86-ad3a-5ad5fc14ac3f}"
    }
  }
}