Add disambiguation to Export, linking to GDScript/C# exports

tutorials/export/index.rst

@@ -3,6 +3,12 @@
 Export
 ======
 
+.. seealso::
+
+   This section is about exporting a build of your project. If you're trying
+   to export properties from a script, see :ref:`doc_gdscript_exports` or 
+   :ref:`doc_c_sharp_exports`.
+
 .. toctree::
    :maxdepth: 1
    :name: toc-learn-workflow-export