Add tutorial codecrafters-io#22

Author: danistefanovic

README.md

@@ -9,6 +9,7 @@
   * [**Java**: *How to create your own simple 3D render engine in pure Java*](http://blog.rogach.org/2015/08/how-to-create-your-own-simple-3d-render.html)
 
 * Build your own **Blockchain** / **Cryptocurrency** 
+  * [**ATS**: *Functional Blockchain*](https://beta.observablehq.com/@galletti94/functional-blockchain)
   * [**Ethereum**: *From “What is Blockchain?” to building a blockchain in less than an hour*](https://medium.freecodecamp.org/from-what-is-blockchain-to-building-a-blockchain-within-an-hour-4e738efc819d)
   * [**Java**: *Creating Your First Blockchain with Java*](https://medium.com/programmers-blockchain/create-simple-blockchain-java-tutorial-from-scratch-6eeed3cb03fa)
   * [**JavaScript**: *A cryptocurrency implementation in less than 1500 lines of code*](https://github.com/conradoqg/naivecoin)