Update external_editor.rst: point out C# instructions

(cherry picked from commit 1388882b3e359a11c1e0f9f1f9b5590112fc47fa)

tutorials/editor/external_editor.rst

@@ -5,6 +5,11 @@ Using an external text editor
 
 This page explains how to code using an external text editor.
 
+.. note::
+
+    To code C# in an external editor, see
+    :ref:`the C# guide to configure an external editor <doc_c_sharp_setup_external_editor>`.
+
 Godot can be used with an external text editor, such as Sublime Text or Visual
 Studio Code. Browse to the relevant editor settings:
 **Editor > Editor Settings > Text Editor > External**

tutorials/scripting/c_sharp/c_sharp_basics.rst

@@ -55,6 +55,8 @@ If you are building Godot from source, make sure to follow the steps to enable
 .NET support in your build as outlined in the :ref:`doc_compiling_with_dotnet`
 page.
 
+.. _doc_c_sharp_setup_external_editor:
+
 Configuring an external editor
 ------------------------------