Sync docs (readme<->extending re: open/template)

docs/ja_JP.UTF-8/EXTENDING.txt

@@ -5,7 +5,7 @@
          Copyright © 2002-2023 by various contributors; AUTHORS.txt 参照.
                              https://tuxpaint.org/
 
-                                   2023年2月12日
+                                   2023年5月29日
 
                   +------------------------------------------+
                   |目次                                        |
@@ -760,6 +760,12 @@ Template Options
    Options", above. (Note: Tux Paint prior to version 0.9.29 did not support
    starter options.)
 
+   💡 It's also possible to create basic Templates (with no options) from
+   existing saved drawings directly within Tux Paint, from the "Open" dialog.
+   They will be placed in the user's personal templates folder. (Note: Tux
+   Paint prior to version 0.9.31 did not support Template creation from the
+   Open dialog.)
+
                                   Translations
 
    Tux Paint supports numerous languages, thanks to use of the "gettext"