Update README.md

Author: rcalago

core-java-modules/core-java-concurrency-2/README.md

@@ -9,3 +9,4 @@
 - [Parallelize for Loop in Java](https://www.baeldung.com/java-for-loop-parallel)
 - [How to Effectively Unit Test CompletableFuture](https://www.baeldung.com/java-completablefuture-unit-test)
 - [How to Collect All Results and Handle Exceptions With CompletableFuture in a Loop](https://www.baeldung.com/java-completablefuture-collect-results-handle-exceptions)
+- [CompletableFuture runAsync() vs. supplyAsync() in Java](https://www.baeldung.com/java-completablefuture-runasync-supplyasync)