Examine source code of ftime.app

{
  "manifest_version": 2,
  "name": "ftime.app",
  "version": "1.8",
  "description": "Time differences made easy",
  "homepage_url": "https://ftime.app/",
  "icons": {
    "16": "icon-16.png",
    "32": "icon-32.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "browser_action": {
    "default_title": "ftime.app",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon-16.png",
      "32": "icon-32.png",
      "48": "icon-48.png",
      "128": "icon-128.png"
    }
  }
}