Examine source code of Start page

{
  "manifest_version": 3,
  "name": "Start page",
  "homepage_url": "https://github.com/diegorezm/wallpapercl",
  "version": "1.1",
  "description": "A starter page built for you browser!",
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "icons": {
    "16": "favicon-16.png",
    "48": "favicon-48.png",
    "128": "favicon-128.png"
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "diegorezm_startpage@domain.com"
    }
  }
}