refs #1235: i18n: 'uri' and 'alt' attribute on 'image' and 'figure' nodes can be translated if gettext_additional_targets has 'image'.

doc/config.rst

@@ -497,6 +497,9 @@ documentation on :ref:`intl` for details.
    :literal-block: literal blocks: ``::`` and ``code-block``.
    :doctest-block: doctest block
    :raw: raw content
+   :image: image/figure uri and alt
+
+   For example: ``gettext_additional_targets = ['literal-block', 'image']``.
 
    The default is ``[]``.