Examine source code of GeoGuessr timer

{
  "name": "GeoGuessr timer",
  "version": "1.1.2",
  "description": "This extension adds timers to GeoGuessr score bar",
  "manifest_version": 2,
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "js": [
        "src/play.js"
      ],
      "matches": [
        "https://geoguessr.com/*",
        "https://www.geoguessr.com/*"
      ],
      "run_at": "document_start"
    }
  ],
  "icons": {
    "16": "img/icon-16.png",
    "32": "img/icon-32.png",
    "48": "img/icon-48.png",
    "128": "img/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "geoguessr-timer@lamant.io"
    }
  },
  "options_ui": {
    "page": "src/settings.html"
  },
  "browser_action": {
    "default_title": "GeoGuessr Timer",
    "default_popup": "src/settings.html"
  }
}