Update README.md

Author: rcalago

core-kotlin-modules/core-kotlin-collections-6/README.md

@@ -3,4 +3,5 @@
 - [Iterate a Collection Referencing Previous Element in Kotlin](https://www.baeldung.com/kotlin/collection-previous-element)
 - [Sorting List with String Dates in Kotlin](https://www.baeldung.com/kotlin/sort-list-string-dates)
 - [Difference Between eachCount() and eachCountTo() Methods in Kotlin](https://www.baeldung.com/kotlin/eachcount-eachcountto)
+- [Parallel Operations on Kotlin Collections](https://www.baeldung.com/kotlin/collections-parallel-operations)
 - More articles: [[<-- prev]](../core-kotlin-collections-5)