Examine source code of Invoice icon

{
  "manifest_version": 2,
  "name": "Invoice icon",
  "version": "1.0",
  "description": "Invoice icons usually represent types of documents such as: sales invoices, electronic invoices, payment vouchers, etc.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html",
    "default_title": "Click me!"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1cd2d620-7854-445b-a014-8773fa162c76}"
    }
  }
}