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/instance.spec.js

@@ -8,9 +8,9 @@ describe('instance', function () {
   });
 
   it('should have the same methods as default instance', function () {
-    var instance = axios.create();
+    const instance = axios.create();
 
-    for (var prop in axios) {
+    for (const prop in axios) {
       if ([
         'Axios',
         'AxiosError',
@@ -35,7 +35,7 @@ describe('instance', function () {
   });
 
   it('should make an http request without verb helper', function (done) {
-    var instance = axios.create();
+    const instance = axios.create();
 
     instance('/foo');
 
@@ -46,7 +46,7 @@ describe('instance', function () {
   });
 
   it('should make an http request with url instead of baseURL', function (done) {
-    var instance = axios.create({
+    const instance = axios.create({
       url: 'https://api.example.com'
     });
 
@@ -59,7 +59,7 @@ describe('instance', function () {
   });
 
   it('should make an http request', function (done) {
-    var instance = axios.create();
+    const instance = axios.create();
 
     instance.get('/foo');
 
@@ -70,7 +70,7 @@ describe('instance', function () {
   });
 
   it('should use instance options', function (done) {
-    var instance = axios.create({ timeout: 1000 });
+    const instance = axios.create({ timeout: 1000 });
 
     instance.get('/foo');
 
@@ -81,7 +81,7 @@ describe('instance', function () {
   });
 
   it('should have defaults.headers', function () {
-    var instance = axios.create({
+    const instance = axios.create({
       baseURL: 'https://api.example.com'
     });
 
@@ -95,13 +95,13 @@ describe('instance', function () {
       return config;
     });
 
-    var instance = axios.create();
+    const instance = axios.create();
     instance.interceptors.request.use(function (config) {
       config.bar = true;
       return config;
     });
 
-    var response;
+    let response;
     instance.get('/foo').then(function (res) {
       response = res;
     });
@@ -120,10 +120,10 @@ describe('instance', function () {
   });
 
   it('should have getUri on the instance', function() {
-    var instance = axios.create({
+    const instance = axios.create({
       baseURL: 'https://api.example.com'
     });
-    var options = {
+    const options = {
       url: 'foo/bar',
       params: {
         name: 'axios'
@@ -133,8 +133,8 @@ describe('instance', function () {
   });
 
   it('should correctly build url without baseURL', function () {
-    var instance = axios.create();
-    var options = {
+    const instance = axios.create();
+    const options = {
       url: 'foo/bar?foo=bar',
       params: {
         name: 'axios'
@@ -144,8 +144,8 @@ describe('instance', function () {
   });
 
   it('should correctly discard url hash mark', function () {
-    var instance = axios.create();
-    var options = {
+    const instance = axios.create();
+    const options = {
       baseURL: 'https://api.example.com',
       url: 'foo/bar?foo=bar#hash',
       params: {