Merge pull request codecrafters-io#934 from Gokul2003g/broken-link

Fix: Replaced a broken link with alternative from smashingmagazine.com

README.md

@@ -82,7 +82,7 @@ It's a great way to learn.
 * [**JavaScript**: _Learn & Build a JavaScript Blockchain_](https://medium.com/digital-alchemy-holdings/learn-build-a-javascript-blockchain-part-1-ca61c285821e)
 * [**JavaScript**: _Creating a blockchain with JavaScript_](https://github.com/SavjeeTutorials/SavjeeCoin)
 * [**JavaScript**: _How To Launch Your Own Production-Ready Cryptocurrency_](https://hackernoon.com/how-to-launch-your-own-production-ready-cryptocurrency-ab97cb773371)
-* [**JavaScript**: _Writing a Blockchain in Node.js_](https://www.hackdoor.io/articles/writing-a-blockchain-in-nodejs-6512fec33307)
+* [**JavaScript**: _Writing a Blockchain in Node.js_](https://www.smashingmagazine.com/2020/02/cryptocurrency-blockchain-node-js/)
 * [**Kotlin**: _Let’s implement a cryptocurrency in Kotlin_](https://medium.com/@vasilyf/lets-implement-a-cryptocurrency-in-kotlin-part-1-blockchain-8704069f8580)
 * [**Python**: _Learn Blockchains by Building One_](https://hackernoon.com/learn-blockchains-by-building-one-117428612f46)
 * [**Python**: _Build your own blockchain: a Python tutorial_](http://ecomunsing.com/build-your-own-blockchain)