Examine source code of sales tax for amazon

{
  "manifest_version": 3,
  "name": "True Price",
  "version": "1.0",
  "description": "Shows the true price including tax for Amazon.com",
  "browser_specific_settings": {
    "gecko": {
      "id": "trueprice-addon@yourname.local",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "action": {
    "default_icon": {
      "16": "images/icon16.png",
      "48": "images/icon48.png",
      "128": "images/icon128.png"
    },
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "images/icon16.png",
    "48": "images/icon48.png",
    "128": "images/icon128.png"
  },
  "content_scripts": [
    {
      "js": [
        "content.js"
      ],
      "matches": [
        "*://*.amazon.com/*"
      ]
    }
  ],
  "permissions": [
    "storage"
  ]
}