Set the correct file structure to maintain backward compatibility. (#18)

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNodeExt.kt

@@ -0,0 +1,25 @@
+package com.github.adriankuta.datastructure.tree
+
+import kotlin.jvm.JvmSynthetic
+
+typealias ChildDeclaration<T> = ChildDeclarationInterface<T>.() -> Unit
+
+/**
+ * This method can be used to initialize new tree.
+ * ```
+ * val root = tree("World") { ... }
+ * ```
+ * @param root Root element of new tree.
+ * @see [ChildDeclarationInterface.child]
+ */
+@JvmSynthetic
+inline fun <reified T> tree(
+    root: T,
+    defaultIterator: TreeNodeIterators = TreeNodeIterators.PreOrder,
+    childDeclaration: ChildDeclaration<T>
+): TreeNode<T> {
+    val treeNode = TreeNode(root)
+    treeNode.defaultIterator = defaultIterator
+    treeNode.childDeclaration()
+    return treeNode
+}