Update README.md

Author: rcalago

core-kotlin-modules/core-kotlin-collections-5/README.md

@@ -7,3 +7,4 @@ This module contains articles about core Kotlin collections.
 - [Remove Elements From a List While Iterating in Kotlin](https://www.baeldung.com/kotlin/list-remove-elements-while-iterating)
 - [How to Start a for Loop From a Given Index in Kotlin](https://www.baeldung.com/kotlin/for-loop-from-index)
 - [Determine if All Elements Are the Same in a Kotlin List](https://www.baeldung.com/kotlin/list-all-elements-equal-check)
+- [Convert an Array to a String](https://www.baeldung.com/kotlin/array-string-conversion)