chore: Update README.md with RxJS library description

Author: manthanank

README.md

@@ -1,5 +1,7 @@
 # Learn Rxjs
 
+This repository contains the code examples for the RxJS library. RxJS is a library for reactive programming using Observables, to make it easier to compose asynchronous or callback-based code.
+
 [![NPM Package](https://github.com/manthanank/learn-rxjs/actions/workflows/publish.yml/badge.svg)](https://github.com/manthanank/learn-rxjs/actions/workflows/publish.yml)
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