Examine source code of Screenshot Mosaic Maker

{
  "manifest_version": 3,
  "name": "Screenshot Mosaic Maker",
  "version": "1.0",
  "description": "Select area → create mosaic.",
  "permissions": [
    "tabs",
    "activeTab",
    "scripting"
  ],
  "action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "screenshot-mosaic@example.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}