Examine source code of Private Frame

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "version": "0.1",
  "default_locale": "en",
  "icons": {
    "48": "icon.svg"
  },
  "developer": {
    "name": "iiizio"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "PrivateFrame@iiizio",
      "strict_min_version": "67.0a1"
    }
  },
  "permissions": [
    "theme"
  ],
  "background": {
    "scripts": [
      "pf.js"
    ]
  }
}