Add gradle task to generate next day

From kotlin-hands-on/advent-of-code-kotlin-template#17

Author: micheljung

build.gradle.kts

@@ -13,3 +13,33 @@ tasks {
         gradleVersion = "8.5"
     }
 }
+
+task("generateNextDay") {
+    doLast {
+        val prevDayNum = fileTree("$projectDir/src").matching {
+            include("Day*.kt")
+        }.maxOf {
+            val (prevDayNum) = Regex("Day(\\d\\d)").find(it.name)!!.destructured
+            prevDayNum.toInt()
+        }
+        val newDayNum = String.format("%02d", prevDayNum + 1)
+        File("$projectDir/src", "Day$newDayNum.kt").writeText(
+                """
+fun main() {
+    fun part1(input: List<String>): Int {
+        return 0
+    }
+    fun part2(input: List<String>): Int {
+        return 0
+    }
+    // test if implementation meets criteria from the description, like:
+    val testInput = readInput("resources/Day${newDayNum}_test")
+    check(part1(testInput) == 0)
+    val input = readInput("resources/Day$newDayNum")
+    println(part1(input))
+    println(part2(input))
+}
+"""
+        )
+    }
+}