docs/add-new-methods (#12)

Author: johnfercher

README.md

@@ -34,6 +34,8 @@ go get -u github.com/johnfercher/go-tree
 * [AddNext](https://pkg.go.dev/github.com/johnfercher/go-tree/tree#Node.AddNext)
 * [Backtrack](https://pkg.go.dev/github.com/johnfercher/go-tree/tree#Node.Backtrack)
 * [Get](https://pkg.go.dev/github.com/johnfercher/go-tree/tree#Node.Get)
+* [GetNexts](https://pkg.go.dev/github.com/johnfercher/go-tree/tree#Node.GetNexts)
+* [GetPrevious](https://pkg.go.dev/github.com/johnfercher/go-tree/tree#Node.GetPrevious)
 * [GetStructure](https://pkg.go.dev/github.com/johnfercher/go-tree/tree#Node.GetStructure)
 * [IsLeaf](https://pkg.go.dev/github.com/johnfercher/go-tree/tree#Node.IsLeaf)
 * [IsRoot](https://pkg.go.dev/github.com/johnfercher/go-tree/tree#Node.IsLeaf)

tree/example_test.go

@@ -133,6 +133,18 @@ func ExampleNode_GetNexts() {
 	// Do more things
 }
 
+// ExampleNode_GetPrevious demonstrates how to retrieve next nodes from node.
+func ExampleNode_GetPrevious() {
+	root := tree.NewNode(0, "root")
+	leaf := tree.NewNode(1, "leaf")
+
+	root.AddNext(leaf)
+	previous := leaf.GetPrevious()
+	fmt.Println(previous.Get())
+
+	// Do more things
+}
+
 // ExampleNode_IsRoot demonstrates how to retrieve info if node is root.
 func ExampleNode_IsRoot() {
 	n := tree.NewNode(0, 'b')