Examine source code of Sunset background New Tab

{
  "name": "Sunset background",
  "description": "Sunset background",
  "version": "170085295",
  "browser_specific_settings": {
    "gecko": {
      "id": "{fedbf205-f54b-498c-820d-5a7c0238b010}"
    }
  },
  "manifest_version": 3,
  "offline_enabled": true,
  "icons": {
    "128": "icons/icon128.png"
  },
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "chrome_settings_overrides": {
    "homepage": "index.html"
  },
  "action": {
    "default_title": "New Tab"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}