Add valid palindrome solution

Author: hyunjung-choi

valid-palindrome/hyunjung-choi.kt

@@ -0,0 +1,9 @@
+import java.util.Locale.getDefault
+
+class Solution {
+    fun isPalindrome(s: String): Boolean {
+        if (s.isBlank()) return true
+        val cleanedString = s.trim().filter { it.isLetterOrDigit() }.lowercase(getDefault())
+        return cleanedString == cleanedString.reversed()
+    }
+}