housekeeping: upgrade to babel@7 (via #5450)

* Babel 7

* preserve module output; straighten out ES/CJS syntax

* add webpack TODOs

* remove unused Babel modules

* Update index.js

* install @babel/register

src/core/plugins/oas3/wrap-components/model.jsx

@@ -1,7 +1,7 @@
 import React, { Component } from "react"
 import PropTypes from "prop-types"
 import { OAS3ComponentWrapFactory } from "../helpers"
-import { Model } from "core/components/model"
+import Model from "core/components/model"
 
 class ModelComponent extends Component {
   static propTypes = {