fix(Docs): Add babel-polyfill so that the Docs work in IE11 (#2884)

* Add babel-polyfill to docs.

* Babel 7.

* useBuiltIns?

* Remove useBuiltIns.

docs/src/index.js

@@ -1,3 +1,5 @@
+import 'babel-polyfill'
+
 import React from 'react'
 import ReactDOM from 'react-dom'
 import { AppContainer } from 'react-hot-loader'

package.json

@@ -90,6 +90,7 @@
     "babel-plugin-lodash": "^3.2.11",
     "babel-plugin-transform-react-handled-props": "^1.0.0",
     "babel-plugin-transform-react-remove-prop-types": "^0.4.13",
+    "babel-polyfill": "7.0.0-beta.3",
     "chai": "^4.1.1",
     "chai-enzyme": "beta",
     "connect-history-api-fallback": "^1.3.0",

yarn.lock

@@ -1282,6 +1282,13 @@ babel-plugin-transform-react-remove-prop-types@^0.4.13:
   version "0.4.13"
   resolved "https://registry.yarnpkg.com/babel-plugin-transform-react-remove-prop-types/-/babel-plugin-transform-react-remove-prop-types-0.4.13.tgz#331cfc05099a808238311d78319c27460d481189"
 
+babel-polyfill@7.0.0-beta.3:
+  version "7.0.0-beta.3"
+  resolved "https://registry.yarnpkg.com/babel-polyfill/-/babel-polyfill-7.0.0-beta.3.tgz#053f0943cdf498910cc037de2ffc7b1f2e36223a"
+  dependencies:
+    core-js "^2.4.0"
+    regenerator-runtime "^0.11.0"
+
 babel-runtime@^6.22.0, babel-runtime@^6.26.0, babel-runtime@^6.9.2:
   version "6.26.0"
   resolved "https://registry.yarnpkg.com/babel-runtime/-/babel-runtime-6.26.0.tgz#965c7058668e82b55d7bfe04ff2337bc8b5647fe"