Examine source code of Weather Customize

{
  "name": "__MSG_extensionName__",
  "short_name": "__MSG_extensionName__",
  "version": "5.0.9",
  "description": "__MSG_extensionDescription__",
  "icons": {
    "48": "img/icon48.png",
    "128": "img/icon128.png"
  },
  "background": {
    "page": "background.html",
    "persistent": true
  },
  "browser_action": {
    "default_icon": {
      "38": "img/icon38.png"
    },
    "default_title": "Weather",
    "default_popup": "popup.html"
  },
  "manifest_version": 2,
  "permissions": [
    "alarms",
    "storage",
    "geolocation",
    "notifications",
    "idle"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8646a6f3-6274-486c-b775-4e808bfa9ce6}"
    }
  }
}