Select the Emacs learn-by-doing tutorial.
If there is a tutorial version written in the language
of the selected language environment, that version is used.
If there's no tutorial in that language, `TUTORIAL' is selected.
With ARG, you are asked to choose which language.
If DONT-ASK-FOR-REVERT is non-nil the buffer is reverted without
any question when restarting the tutorial.
If any of the standard Emacs key bindings that are used in the
tutorial have been changed then an explanatory note about this is
shown in the beginning of the tutorial buffer.
When the tutorial buffer is killed the content and the point
position in the buffer is saved so that the tutorial may be
resumed later.
(fn &optional ARG DONT-ASK-FOR-REVERT)