Examine source code of Page Load Timer

{
  "manifest_version": 3,
  "name": "Page Load Timer",
  "version": "0.0.9",
  "description": "Displays webpage load time in the toolbar",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "3af30ce3ca06fe7a53f9b7692598def4eabd66da@pageloadtime"
    }
  },
  "action": {
    "default_icon": "stopwatch48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "browser-polyfill.min.js",
        "performance.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "activeTab",
    "storage"
  ],
  "host_permissions": [
    "*://*/*"
  ],
  "icons": {
    "48": "stopwatch48.png",
    "96": "stopwatch96.png",
    "128": "stopwatch128.png"
  }
}