Mention documentation comments in GDScript basics

tutorials/scripting/gdscript/gdscript_basics.rst

@@ -572,6 +572,12 @@ considered a comment.
  The list of highlighted keywords and their colors can be changed in the **Text
  Editor > Theme > Comment Markers** section of the Editor Settings.
 
+It is also possible to mark certain comments as :ref:`documentation comments <doc_gdscript_documentation_comments>`
+by using two hash symbols (``##``) instead of one (``#``). This only has an
+effect for comments placed immediately *above* a documentable item (such as a
+member variable), or at the top of a file. Dedicated formatting options are also
+available. See :ref:`doc_gdscript_documentation_comments` for details.
+
 Code regions
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