kt: add «151. Reverse Words in a String»

URL:	https://leetcode.com/problems/reverse-words-in-a-string/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/reverse-words-in-a-string.kt

@@ -0,0 +1,3 @@
+class Solution {
+    fun reverseWords(s: String): String = s.trim().split(Regex("\\s+")).reversed().joinToString(" ")
+}