Examine source code of postLogger

{
  "name": "postLogger",
  "version": "1.4",
  "description": "Extension to log postMessage()",
  "icons": {
    "48": "icon48.png"
  },
  "content_scripts": [
    {
      "all_frames": true,
      "run_at": "document_start",
      "match_about_blank": true,
      "match_origin_as_fallback": true,
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "WindowScript.js"
      ],
      "world": "MAIN"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "postlogger@ndevtk"
    }
  },
  "manifest_version": 3
}