Examine source code of WebPDF

{
  "manifest_version": 2,
  "name": "WebPDF",
  "version": "1.0",
  "description": "Download web page as PDF document",
  "icons": {
    "48": "icons/export-pdf-48.png",
    "96": "icons/export-pdf-96.png"
  },
  "background": {
    "scripts": [
      "background-script.js"
    ],
    "type": "module"
  },
  "browser_action": {
    "default_icon": {
      "48": "icons/export-pdf-48.png",
      "96": "icons/export-pdf-96.png"
    },
    "default_title": "Download web page as PDF document"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f060c8d9-b6b1-4d0e-94f5-43ee248be57f}"
    }
  }
}