Add C# to Scene Tree Page

getting_started/step_by_step/scene_tree.rst

@@ -75,11 +75,17 @@ The root :ref:`Viewport <class_Viewport>`
 is always at the top of the scene. From a node, it can be obtained in
 two different ways:
 
-::
+.. tabs::
+ .. code-tab:: gdscript GDScript
 
         get_tree().get_root() # access via scenemainloop
         get_node("/root") # access via absolute path
 
+ .. code-tab:: csharp
+
+        GetTree().GetRoot(); // access via scenemainloop
+        GetNode("/root"); // access via absolute path
+
 This node contains the main viewport, anything that is a child of a
 :ref:`Viewport <class_Viewport>`
 is drawn inside of it by default, so it makes sense that the top of all
@@ -140,10 +146,18 @@ another one. The simple way to do this is to use the
 :ref:`SceneTree.change_scene() <class_SceneTree_change_scene>`
 function:
 
-::
+.. tabs::
+ .. code-tab:: gdscript GDScript
 
     func _my_level_was_completed():
-        get_tree().change_scene("res://levels/level2.tscn")
+    	get_tree().change_scene("res://levels/level2.tscn")
+
+ .. code-tab:: csharp
+
+    public void _MyLevelWasCompleted()
+    {
+        GetTree().ChangeScene("res://levels/level2.tscn");
+    }
 
 This is a quick and useful way to switch scenes, but has the drawback
 that the game will stall until the new scene is loaded and running. At