Add Kotlin solution to day 8 part 1

src/Day08.kt

@@ -0,0 +1,40 @@
+fun main() {
+    fun part1(input: List<String>): Int {
+        val stepOrder = input.first()
+        val nodes = input.slice(2..input.lastIndex).toNodes()
+        var currentNode = "AAA"
+        var stepIndex = 0
+        var steps = 0
+        while (currentNode != "ZZZ") {
+            val step = stepOrder[stepIndex]
+            currentNode = nodes.require(currentNode).require(step)
+            steps++
+            if (++stepIndex == stepOrder.length) {
+                stepIndex = 0
+            }
+        }
+        return steps
+    }
+
+    fun part2(input: List<String>): Int {
+        throw RuntimeException("Day 8 part 2 was done in lua, see Day08.lua")
+    }
+
+    // test if implementation meets criteria from the description, like:
+    val testInput = readInput("Day08_test")
+    check(part2(testInput) == 6)
+
+    val input = readInput("Day08")
+    part1(input).println()
+    part2(input).println()
+}
+
+fun List<String>.toNodes(): Map<String, Map<Char, String>> = associate { line ->
+    val letterGroups = Regex("\\w+").findAll(line).map { it.value }.toList()
+    letterGroups.first() to mapOf(
+        'L' to letterGroups[1],
+        'R' to letterGroups[2],
+    )
+}
+
+fun <K, V> Map<K, V>.require(key: K): V = requireNotNull(get(key))