Examine source code of ATK Better Print

{
  "manifest_version": 3,
  "name": "ATK Better Print",
  "version": "1.4",
  "description": "Customizable print view for America's Test Kitchen recipes.",
  "host_permissions": [
    "*://*.americastestkitchen.com/*",
    "*://*.cooksillustrated.com/*",
    "*://*.cookscountry.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.americastestkitchen.com/*",
        "*://*.cooksillustrated.com/*",
        "*://*.cookscountry.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "content_security_policy": {
    "extension_pages": "script-src 'self'; object-src 'none';"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "atk-printer@yourname.local",
      "strict_min_version": "115.0"
    }
  }
}