Examine source code of Calcupain

{
  "manifest_version": 3,
  "name": "Calcupain",
  "version": "1.3.1",
  "description": "A quick way to calculate the time to charge the customer",
  "icons": {
    "16": "img/baguette-16.png",
    "32": "img/baguette-32.png",
    "48": "img/baguette-48.png",
    "96": "img/baguette-96.png",
    "128": "img/baguette-128.png"
  },
  "action": {
    "default_title": "Calcupain",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{dc0fd736-a34d-4519-b069-26cd67966f71}"
    }
  }
}