Examine source code of Theme Travel

{
  "description": "Check user time and then you will see new travel theme every hour.",
  "homepage_url": "https://github.com/nabendu82/Addons",
  "icons": {
    "48": "icons/logo_48.png",
    "64": "icons/logo_64.png"
  },
  "manifest_version": 2,
  "name": "Theme Travel",
  "permissions": [
    "alarms",
    "theme"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "version": "1.0",
  "applications": {
    "gecko": {
      "strict_min_version": "55.0a2",
      "id": "{4ec7aaed-1ee4-4efe-ac0c-9dc7cf629567}"
    }
  }
}