feat(build): es2015 bundle artifact (#6291)

* es2015 bundle with dependencies via npm script build:es:bundle
* es2015 bundle without dependencies via npm script build:es:bundle
* jest dependency for test:artifact
* migrate babel.config.json to babel.config.js and maintain env support for commonjs and es2015
* remove polyfill
* fix es syntax: replace module.exports with export
* fix es syntax: remove .jsx extension inside import

test/build-artifacts/umd.js

@@ -0,0 +1,8 @@
+import { describe, expect, test } from '@jest/globals';
+import SwaggerUI from '../../dist/swagger-ui-bundle';
+
+describe('webpack browser umd build', () => {
+  test('should export a function for (umd) bundle', () => {
+    expect(SwaggerUI).toBeInstanceOf(Function);
+  });
+});