fix(react): add back CC imports due to potential stencil bug (#269)

There is an issue with auto-importing and defining calcite components
using the react wrapper via
Esri/calcite-design-system#7185

It appears to be a Stencil bug related to our SSR patch which
dynamically imports the web components to prevent them from rendering on
the server.
Esri/calcite-design-system#7521

react/src/App.js

@@ -1,4 +1,7 @@
 import React, { useState } from 'react';
+import "@esri/calcite-components/dist/components/calcite-button.js";
+import "@esri/calcite-components/dist/components/calcite-icon.js";
+import "@esri/calcite-components/dist/components/calcite-slider.js";
 import {
   CalciteButton,
   CalciteIcon,