Examine source code of Zen Mode

{
  "manifest_version": 2,
  "name": "Zen Mode",
  "version": "1.0.0",
  "description": "Distraction-free reading",
  "icons": {
    "48": "icons/icon48.png"
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_popup": "popup/popup.html",
    "default_icon": "icons/icon48.png"
  },
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "zenmode@extensions.local",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}