docs(assertion): add Supertest JavaScript assertion library (#911)

A popular HTTP assertion library for testing REST APIs, often used with other testing frameworks like Mocha or Jest

Author: ChyzhykTech

README.md

@@ -169,6 +169,7 @@ A collection of awesome browser-side [JavaScript](https://developer.mozilla.org/
 * [Sinon.JS](https://github.com/sinonjs/sinon) - Test spies, stubs, and mocks for JavaScript.
 * [expect.js](https://github.com/Automattic/expect.js) - Minimalistic BDD-style assertions for Node.JS and the browser.
 * [proxyquire](https://github.com/thlorenz/proxyquire) - Stub nodejs's require.
+* [Supertest](https://github.com/visionmedia/supertest) - A popular HTTP assertion library for testing REST APIs, often used with other testing frameworks like Mocha or Jest
 
 ### Coverage