**Please do not work on this issue unless you have applied to the outreachy project.**

The [pageviewer.js](https://github.com/mozilla/pdf.js/blob/master/examples/components/pageviewer.js) example currently uses the older style of `promise.then` and callbacks. Convert it to use an `async` function and `await` style.

*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http:www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
"use strict";
if (!pdfjsLib.getDocument || !pdfjsViewer.PDFPageView) {
  
  alert("Please build the pdfjs-dist library using\n  `gulp dist-install`");
}
pdfjsLib.GlobalWorkerOptions.workerSrc =
  "../../node_modules/pdfjs-dist/build/pdf.worker.js";
const CMAP_URL = "../../node_modules/pdfjs-dist/cmaps/";
const CMAP_PACKED = true;
const DEFAULT_URL = "../../web/compressed.tracemonkey-pldi-09.pdf";
const PAGE_TO_VIEW = 1;
const SCALE = 1.0;
const ENABLE_XFA = true;
const container = document.getElementById("pageContainer");
const eventBus = new pdfjsViewer.EventBus();
const loadingTask = pdfjsLib.getDocument({
  url: DEFAULT_URL,