Examine source code of Tab Pad - New Tab Notepad

{
  "update_url" : "https://clients2.google.com/service/update2/crx" ,
  "manifest_version" : 3 ,
  "name" : "Tab Pad - New Tab Notepad",
  "version" : "1.2.2",
  "description" : "Your daily notepad, one page per day, in every new tab. Everything stays on your device.",
  "chrome_url_overrides" : {
    "newtab" : "index.html"
  },
  "permissions" : [],
  "optional_permissions" : [
    "nativeMessaging" 
  ],
  "content_security_policy" : {
    "extension_pages": "script-src 'self'; object-src 'self'; img-src 'self' data:"
  },
  "icons" : {
    "16" : "icons/16.png",
    "32" : "icons/32.png",
    "48" : "icons/48.png",
    "128" : "icons/128.png"
  }
}