Examine source code of Dynamic Background

{
  "manifest_version": 2,
  "name": "Dynamic Background",
  "version": "1.0",
  "description": "Changes the background of the Firefox New Tab page based on the time of day or current weather.",
  "permissions": [
    "storage",
    "geolocation"
  ],
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "icons": {
    "16": "icons/icon.png",
    "48": "icons/icon.png",
    "128": "icons/icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d65bc3f3-5ed7-4c8a-8884-2c8e05d84f0c}"
    }
  }
}