Subject: Add example of setting view-exit-action to a "function with one argument"

From: 積丹尼 Dan Jacobson <[email-masked]>
Date: Sun, 05 May 2019 20:26:55 +0800

view-exit-action is a variable defined in ‘view.el’.
   Its value is nil

     Automatically becomes buffer-local when set.

   Documentation:
   If non-nil, a function with one argument (a buffer) called when finished viewing.

Better add an example of how to set "a function with one argument". Thanks.