Examine source code of Price rounder for Amazon

{
  "manifest_version": 3,
  "version": "1.2.1",
  "name": "Price rounder for Amazon",
  "short_name": "Price rounder",
  "description": "Rounds up prices on Amazon",
  "icons": {
    "32": "icons/32.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2b41fad3-0e6f-4361-a108-12d0eec39bec}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "storage"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": "icons/32.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.amazon.com/*",
        "*://*.amazon.com.au/*",
        "*://*.amazon.com.be/*",
        "*://*.amazon.com.br/*",
        "*://*.amazon.ca/*",
        "*://*.amazon.cn/*",
        "*://*.amazon.de/*",
        "*://*.amazon.eg/*",
        "*://*.amazon.fr/*",
        "*://*.amazon.in/*",
        "*://*.amazon.ie/*",
        "*://*.amazon.it/*",
        "*://*.amazon.co.jp/*",
        "*://*.amazon.com.mx/*",
        "*://*.amazon.nl/*",
        "*://*.amazon.pl/*",
        "*://*.amazon.sa/*",
        "*://*.amazon.sg/*",
        "*://*.amazon.co.za/*",
        "*://*.amazon.es/*",
        "*://*.amazon.se/*",
        "*://*.amazon.com.tr/*",
        "*://*.amazon.ae/*",
        "*://*.amazon.co.uk/*"
      ],
      "js": [
        "functions.js",
        "script.js"
      ]
    }
  ]
}