Axios ES2017 (#4787)

* Added AxiosHeaders class;

* Fixed README.md href;

* Fixed a potential bug with headers normalization;

* Fixed a potential bug with headers normalization;
Refactored accessor building routine;
Refactored default transforms;
Removed `normalizeHeaderName` helper;

* Added `Content-Length` accessor;
Added missed `has` accessor to TS types;

* Added `AxiosTransformStream` class;
Added progress capturing ability for node.js environment;
Added `maxRate` option to limit the data rate in node.js environment;
Refactored event handled by `onUploadProgress` && `onDownloadProgress` listeners in browser environment;
Added progress & data rate tests for the http adapter;
Added response stream aborting test;
Added a manual progress capture test for the browser;
Updated TS types;
Added TS tests;
Refactored request abort logic for the http adapter;
Added ability to abort the response stream;

* Remove `stream/promises` & `timers/promises` modules usage in tests;

* Use `abortcontroller-polyfill`;

* Fixed AxiosTransformStream dead-lock in legacy node versions;
Fixed CancelError emitting in streams;

* Reworked AxiosTransformStream internal logic to optimize memory consumption;
Added throwing an error if the request stream was silently destroying (without error) Refers to #3966;

* Treat the destruction of the request stream as a cancellation of the request;
Fixed tests;

* Emit `progress` event in the next tick;

* Initial refactoring;

* Refactored Mocha tests to use ESM;

* Refactored Karma tests to use rollup preprocessor & ESM;
Replaced grunt with gulp;
Improved dev scripts;
Added Babel for rollup build;

* Added default commonjs package export for Node build;
Added automatic contributors list generator for package.json;

Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/helpers/formDataToJSON.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var utils = require('../utils');
+import utils from '../utils.js';
 
 /**
  * It takes a string like `foo[x][y][z]` and returns an array like `['foo', 'x', 'y', 'z']
@@ -14,7 +14,7 @@ function parsePropPath(name) {
   // foo.x.y.z
   // foo-x-y-z
   // foo x y z
-  return utils.matchAll(/\w+|\[(\w*)]/g, name).map(function(match) {
+  return utils.matchAll(/\w+|\[(\w*)]/g, name).map(match => {
     return match[0] === '[]' ? '' : match[1] || match[0];
   });
 }
@@ -27,11 +27,11 @@ function parsePropPath(name) {
  * @returns An object with the same keys and values as the array.
  */
 function arrayToObject(arr) {
-  var obj = {};
-  var keys = Object.keys(arr);
-  var i;
-  var len = keys.length;
-  var key;
+  const obj = {};
+  const keys = Object.keys(arr);
+  let i;
+  const len = keys.length;
+  let key;
   for (i = 0; i < len; i++) {
     key = keys[i];
     obj[key] = arr[key];
@@ -48,13 +48,13 @@ function arrayToObject(arr) {
  */
 function formDataToJSON(formData) {
   function buildPath(path, value, target, index) {
-    var name = path[index++];
-    var isNumericKey = Number.isFinite(+name);
-    var isLast = index >= path.length;
+    let name = path[index++];
+    const isNumericKey = Number.isFinite(+name);
+    const isLast = index >= path.length;
     name = !name && utils.isArray(target) ? target.length : name;
 
     if (isLast) {
-      if (utils.hasOwnProperty(target, name)) {
+      if (utils.hasOwnProp(target, name)) {
         target[name] = [target[name], value];
       } else {
         target[name] = value;
@@ -67,7 +67,7 @@ function formDataToJSON(formData) {
       target[name] = [];
     }
 
-    var result = buildPath(path, value, target[name], index);
+    const result = buildPath(path, value, target[name], index);
 
     if (result && utils.isArray(target[name])) {
       target[name] = arrayToObject(target[name]);
@@ -77,9 +77,9 @@ function formDataToJSON(formData) {
   }
 
   if (utils.isFormData(formData) && utils.isFunction(formData.entries)) {
-    var obj = {};
+    const obj = {};
 
-    utils.forEachEntry(formData, function(name, value) {
+    utils.forEachEntry(formData, (name, value) => {
       buildPath(parsePropPath(name), value, obj, 0);
     });
 
@@ -89,4 +89,4 @@ function formDataToJSON(formData) {
   return null;
 }
 
-module.exports = formDataToJSON;
+export default formDataToJSON;