Examine source code of Show Open Tabs

{
  "manifest_version": 2,
  "name": "Show Open Tabs",
  "version": "1.0",
  "description": "Displays a list of all open tabs in Firefox.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6405f5ec-2495-4e8b-9cdb-2073cc186b66}"
    }
  }
}