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

The [node/pdf2png/pdf2png.js](https://github.com/mozilla/pdf.js/blob/master/examples/node/pdf2png/pdf2png.js) example currently uses the older style of `promise.then` and callbacks. Convert it to use an `async` function and `await` style.

/* Copyright 2017 Mozilla Foundation
 *
 * 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.
 */
const Canvas = require("canvas");
const assert = require("assert").strict;
const fs = require("fs");
function NodeCanvasFactory() {}