Examine source code of Weather Extension

{
  "manifest_version": 2,
  "name": "Weather Extension",
  "version": "1.0",
  "description": "Get the current weather for any city.",
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Weather Extension"
  },
  "permissions": [
    "storage",
    "https://api.openweathermap.org/"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e3a0021e-495d-41f6-90c7-8eb9b903040a}"
    }
  }
}