Examine source code of Page Cache

{
  "manifest_version": 2,
  "name": "Page Cache",
  "version": "1.0",
  "description": "Cache pages for indefinite offline access",
  "permissions": [
    "activeTab",
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": {
      "48": "icons/icon-48.svg",
      "96": "icons/icon-96.svg"
    },
    "default_popup": "popup.html",
    "default_title": "Page Cache"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "web_accessible_resources": [
    "viewer.html"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "page-cache@dspyz",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    },
    "gecko_android": {}
  }
}