kt: add «141. Linked List Cycle»

URL:	https://leetcode.com/problems/linked-list-cycle/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/linked-list-cycle.kt

@@ -0,0 +1,16 @@
+class Solution {
+    fun hasCycle(head: ListNode?): Boolean {
+        var (x, y) = head to head
+
+        while (y != null && y!!.next != null) {
+            x = x!!.next
+            y = y!!.next!!.next
+
+            if (x == y) {
+                return true
+            }
+        }
+
+        return false
+    }
+}