Update README.md

Author: mtumilowicz

README.md

@@ -3,7 +3,7 @@
 
 # java12-introduction-to-reactive-programming-workshop
 _Reference_: [Out-of-the-box Reactive Streams with Java 9](https://www.youtube.com/watch?v=COgktgJmP_k)  
-_Reference_: https://github.com/rucek/reactive-streams-java9
+_Reference_: https://github.com/rucek/reactive-streams-java9  
 _Reference_: https://github.com/reactive-streams/reactive-streams-jvm  
 _Reference_: https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/Flow.html