Added data URL support for node.js; (#4725)

* Added data URL support for node.js;
Added missed data URL protocol for the browser environment;
Optimized JSON parsing in the default response transformer;
Refactored project structure;
Added `cause` prop for AxiosError instance that refers to the original error if it was wrapped with `AxiosError.from` method;
Added fromDataURI helper;
Added test for handling data:url as an `arraybuffer|text|stream`;

* Added throwing of 405 HTTP error if the method is not GET;

test/unit/helpers/fromDataURI.js

@@ -0,0 +1,12 @@
+var assert = require('assert');
+var fromDataURI = require('../../../lib/helpers/fromDataURI');
+
+describe('helpers::fromDataURI', function () {
+  it('should return buffer from data uri', function () {
+    const buffer= Buffer.from('123');
+
+    const dataURI = 'data:application/octet-stream;base64,' + buffer.toString('base64');
+
+    assert.deepStrictEqual(fromDataURI(dataURI), buffer);
+  });
+});