Examine source code of Weather Overlay

{
  "manifest_version": 2,
  "name": "Weather Overlay",
  "version": "1.0",
  "description": "Display current weather and forecast on a new tab or in the corner of the web page.",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "geolocation",
    "storage",
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a13091af-8a6d-4d2f-8a30-8530d09fcaf5}"
    }
  }
}