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>

test/specs/utils/forEach.spec.js

@@ -1,8 +1,10 @@
-var forEach = require('../../../lib/utils').forEach;
+import utils from '../../../lib/utils';
+
+const {forEach} = utils;
 
 describe('utils::forEach', function () {
   it('should loop over an array', function () {
-    var sum = 0;
+    let sum = 0;
 
     forEach([1, 2, 3, 4, 5], function (val) {
       sum += val;
@@ -12,9 +14,9 @@ describe('utils::forEach', function () {
   });
 
   it('should loop over object keys', function () {
-    var keys = '';
-    var vals = 0;
-    var obj = {
+    let keys = '';
+    let vals = 0;
+    const obj = {
       b: 1,
       a: 2,
       r: 3
@@ -30,7 +32,7 @@ describe('utils::forEach', function () {
   });
 
   it('should handle undefined gracefully', function () {
-    var count = 0;
+    let count = 0;
 
     forEach(undefined, function () {
       count++;
@@ -40,7 +42,7 @@ describe('utils::forEach', function () {
   });
 
   it('should make an array out of non-array argument', function () {
-    var count = 0;
+    let count = 0;
 
     forEach(function () {}, function () {
       count++;
@@ -50,8 +52,8 @@ describe('utils::forEach', function () {
   });
 
   it('should handle non object prototype gracefully', function () {
-    var count = 0;
-    var data = Object.create(null);
+    let count = 0;
+    const data = Object.create(null);
     data.foo = 'bar'
 
     forEach(data, function () {