Add part3

part3/phonebook/node_modules/async/internal/promiseCallback.js

@@ -0,0 +1,23 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+const PROMISE_SYMBOL = Symbol('promiseCallback');
+
+function promiseCallback() {
+    let resolve, reject;
+    function callback(err, ...args) {
+        if (err) return reject(err);
+        resolve(args.length > 1 ? args : args[0]);
+    }
+
+    callback[PROMISE_SYMBOL] = new Promise((res, rej) => {
+        resolve = res, reject = rej;
+    });
+
+    return callback;
+}
+
+exports.promiseCallback = promiseCallback;
+exports.PROMISE_SYMBOL = PROMISE_SYMBOL;