respect 'output.private' in '-K/--list-keywords' output

docs/configuration.rst

@@ -2792,16 +2792,6 @@ Output Options
 ==============
 
 
-output.fallback
----------------
-Type
-    ``bool``
-Default
-    ``true``
-Description
-    Include fallback URLs in the output of ``-g/--get-urls``.
-
-
 output.mode
 -----------
 Type
@@ -2842,6 +2832,28 @@ Description
     Show skipped file downloads.
 
 
+output.fallback
+---------------
+Type
+    ``bool``
+Default
+    ``true``
+Description
+    Include fallback URLs in the output of ``-g/--get-urls``.
+
+
+output.private
+--------------
+Type
+    ``bool``
+Default
+    ``false``
+Description
+    Include private fields,
+    i.e. fields whose name starts with an underscore,
+    in the output of ``-K/--list-keywords`` and ``-j/--dump-json``.
+
+
 output.progress
 ---------------
 Type