Examine source code of Zen Writer Mode

{
  "manifest_version": 3,
  "name": "__MSG_extensionName__",
  "version": "1.0",
  "description": "__MSG_extensionDescription__",
  "icons": {
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b3f7d3c0-a5e7-1f3b-a5d2-c9f3d3e5b1a5}"
    }
  },
  "permissions": [
    "storage"
  ],
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "128": "icons/icon128.png"
    }
  }
}