Examine source code of Page Cage

{
  "name": "Page Cage",
  "short_name": "Cage",
  "description": "Loads a page inside a frame so it can't be seen by other extensions",
  "version": "0.1.4",
  "manifest_version": 3,
  "icons": {
    "16": "cage-16.png",
    "48": "cage-48.png",
    "128": "cage-128.png"
  },
  "content_security_policy": {
    "extension_pages": "default-src 'self'; frame-src 'self' https://* http://*"
  },
  "permissions": [
    "contextMenus",
    "history"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_icon": {
      "16": "cage-16.png",
      "48": "cage-48.png",
      "128": "cage-128.png"
    },
    "default_title": "Cage"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{000d5e03-3093-485a-a0f3-b406fe4558cd}"
    }
  }
}