Updated free-courses-en.md (#8524)

Updated the Kotlin section with a free Udemy course for beginners

courses/free-courses-en.md

@@ -869,6 +869,7 @@
 * [Kotlin Course - Tutorial for Beginners](https://www.youtube.com/watch?v=F9UC9DY-vIU) - Nate Ebel, freeCodeCamp (YouTube)
 * [Kotlin for Java Developers](https://www.coursera.org/learn/kotlin-for-java-developers) - Svetlana Isakova, Andrey Breslav (Coursera)
 * [Kotlin Newbie To Pro](https://www.youtube.com/playlist?list=PLQkwcJG4YTCRSQikwhtoApYs9ij_Hc5Z9) - Philipp Lackner
+* [One hour Kotlin guide for beginners](https://www.udemy.com/course/one-hour-kotlin-guide-for-beginners) - Tutlets Kkang (Udemy)
 * [Track: Kotlin Basics](https://hyperskill.org/tracks/18) - Hyperskill, JetBrains (Hyperskill)