Add mentor notes Kotlin/Anagram

tracks/kotlin/exercises/anagram/mentoring.md

@@ -0,0 +1,19 @@
+# Mentoring
+
+## Reasonable Solutions
+```kotlin
+class Anagram(var anagram: String){
+    fun match(list: List<String>): Set<String>{
+        return list.filter {
+            it.lowercase() != anagram.lowercase() && it.order() == anagram.order()
+        }.toSet()
+    }
+
+    private fun String.order(): List<Char>{
+        return this.map { it.lowercaseChar() }.sorted()
+    }
+}
+```
+
+## Common suggestions
+* Function `sorted()` can be used to sort according to the characters natural sort order