Examine source code of Text Scramble

{
  "manifest_version": 2,
  "name": "Text Scramble",
  "version": "1.1",
  "description": "Scramble reverse shuffle and mangle text in fun ways",
  "browser_specific_settings": {
    "gecko": {
      "id": "{9ac4cbef-c49d-47a8-b4ec-86c6f7d73025}",
      "strict_min_version": "96.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "assets/icon_16.png",
    "48": "assets/icon_48.png"
  },
  "browser_action": {
    "default_popup": "overlay/overlay.html",
    "default_icon": {
      "16": "assets/icon_16.png",
      "48": "assets/icon_48.png"
    }
  },
  "background": {
    "scripts": [
      "worker/monitor.js"
    ]
  },
  "permissions": []
}