Examine source code of ToDo

{
  "manifest_version": 2,
  "name": "ToDo",
  "description": "__MSG_description__",
  "version": "3.5",
  "default_locale": "en",
  "icons": {
    "16": "assets/icons/16.png",
    "32": "assets/icons/32.png",
    "48": "assets/icons/48.png",
    "128": "assets/icons/128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "options-page/index.html"
  },
  "optional_permissions": [
    "downloads"
  ],
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1c047394-2f2c-4099-abf1-6fe8ee456e94}"
    }
  }
}