Add project description and used tech stack, and link to third course

Author: yamalight

README.md

@@ -6,6 +6,13 @@
 
 This repository contains code and related materials for [Building products with javascript](https://www.youtube.com/playlist?list=PL_gX69xPLi-ljVdNhspjZUlPmBNjRgD2X) course.
 
+## Project description
+
+This is a simple client-server CRUD application that allows users to ask and answer questions.  
+It uses [express.js](https://expressjs.com/), [passport.js](http://passportjs.org/) with [JWT](https://jwt.io/) and [thinky](https://github.com/neumino/thinky) along with [RethinkDB](https://www.rethinkdb.com/) on a backend; [React](https://facebook.github.io/react/), [Redux](http://redux.js.org/), [RxJS](https://github.com/Reactive-Extensions/RxJS) on front-end.  
+Backend is tested using [tape](https://github.com/substack/tape) and [supertest](https://github.com/visionmedia/supertest), while front-end uses [jest](https://facebook.github.io/jest/) and [enzyme](https://github.com/airbnb/enzyme).
+[Docker](https://www.docker.com/) and [docker-compose](https://docs.docker.com/compose/) are used for deployment.
+
 ## CI/CD
 
 CI and CD for all the subprojects is done using [Gitlab-CI](https://gitlab.com/yamalight/building-products-with-js).
@@ -20,7 +27,11 @@ CI and CD for all the subprojects is done using [Gitlab-CI](https://gitlab.com/y
 
 ## Course 2: Building Electron.js apps
 
-My secound course on building Electron.js apps can be found [here](https://github.com/yamalight/bpjs-electron) and [here](https://www.youtube.com/playlist?list=PL_gX69xPLi-lBH8I52J-3nEhEQD6_nDs6).
+My second course on building Electron.js apps can be found [here](https://github.com/yamalight/bpjs-electron) and [here](https://www.youtube.com/playlist?list=PL_gX69xPLi-lBH8I52J-3nEhEQD6_nDs6).
+
+## Course 3: Building Data Science apps
+
+My third course on building data science apps can be found [here](https://github.com/BuildingXwithJS/building-data-science-with-js) and [here](https://www.youtube.com/playlist?list=PL_gX69xPLi-lGe7iRt6DqTZ7PpIrNq8ep).
 
 ## License