Examine source code of UTM Builder

{
  "manifest_version": 2,
  "name": "UTM Builder",
  "description": "UTM-Builder UTM Tagging: speed along with precision when creating trackable links. Sign up at https://app.utm-builder.com",
  "version": "0.4.9",
  "short_name": "Quick UTM Builder.com",
  "author": "Michael O'Toole",
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "activeTab",
    "clipboardWrite",
    "tabs",
    "identity",
    "https://maxcdn.bootstrapcdn.com/",
    "https://app.utm-builder.com/*"
  ],
  "background": {
    "page": "background.html"
  },
  "icons": {
    "16": "icon.png",
    "128": "icon128.png"
  },
  "content_scripts": []
}