@x-govuk/govuk-prototype-components/src/govuk-prototype-kit/init.js

Common and experimental components that are not yet part of the GOV.UK Design System

if (
  window.GOVUKPrototypeKit &&
  window.GOVUKPrototypeKit.documentReady &&
  window.GOVUKPrototypeKit.majorVersion >= 13
) {
  window.GOVUKPrototypeKit.documentReady(function () {
    window.GOVUKPrototypeComponents.initAll()
  })
}