Examine source code of SkyCheck

{
  "manifest_version": 2,
  "name": "SkyCheck",
  "version": "1.0",
  "description": "Check current weather for any city using OpenWeatherMap API.",
  "permissions": [
    "storage",
    "https://api.openweathermap.org/*"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "icons": {
    "16": "icon.png",
    "48": "icon.png",
    "128": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ad660ef0-1f0e-4c47-92c4-5027c865a062}"
    }
  }
}