Examine source code of Sandbox Pay

{
  "manifest_version": 3,
  "name": "__MSG_extName__",
  "description": "__MSG_extDescription__",
  "version": "1.0.0",
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "128": "icon/128.png"
  },
  "default_locale": "en",
  "permissions": [
    "activeTab",
    "scripting",
    "contextMenus",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6bc5b0a9-991e-4b7b-8ab8-ef204f8c953e}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "sidebar_action": {
    "default_panel": "sidepanel.html",
    "default_title": "PayPal Sandbox Cards"
  },
  "action": {},
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.appspot.com/*",
        "*://*.paypal.com/*",
        "*://*.sandbox.paypal.com/*",
        "*://*.stripe.com/*",
        "*://127.0.0.1/*",
        "*://localhost/*"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}