Examine source code of Traffic Router

{
  "manifest_version": 3,
  "name": "Traffic Router",
  "browser_specific_settings": {
    "gecko": {
      "id": "trafficRouter@run1-cs",
      "data_collection_permissions": {
        "required": [
          "browsingActivity",
          "websiteContent",
          "websiteActivity"
        ]
      }
    }
  },
  "version": "0.1.0",
  "description": "Redirects traffic from one domain to another.",
  "permissions": [
    "storage",
    "webRequest",
    "webRequestBlocking"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "content/content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "action": {
    "default_icon": "icon.png",
    "default_title": "Traffic Router",
    "default_popup": "popup/popup.html"
  }
}