Examine source code of jokeextension

{
  "name": "jokes",
  "version": "0.0.1",
  "manifest_version": 2,
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "logo.png"
  },
  "icons": {
    "128": "logo.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1d615eaa-4460-4d19-bd7a-b54438b04787}"
    }
  }
}