Describe desktop package lazy restore feature.

etc/NEWS

@@ -397,20 +397,30 @@ saving.
 *** Buffers are saved in the desktop file in the same order as that in the
 buffer list.
+*** The desktop package can be customized to restore only some buffers immediately,
+remaining buffers are restored lazily (when Emacs is idle).
+
 *** New commands:
   - desktop-revert reverts to the last loaded desktop.
   - desktop-change-dir kills current desktop and loads a new.
   - desktop-save-in-desktop-dir saves desktop in the directory from which
     it was loaded.
+  - desktop-lazy-complete runs the desktop load to completion.
+  - desktop-lazy-abort aborts lazy loading of the desktop.
 *** New customizable variables:
   - desktop-save. Determins whether the desktop should be saved when it is
     killed.
-  - desktop-file-name-format.
+  - desktop-file-name-format. Format in which desktop file names should be saved.
   - desktop-path. List of directories in which to lookup the desktop file.
-  - desktop-locals-to-save.
-  - desktop-globals-to-clear.
-  - desktop-clear-preserve-buffers-regexp.
+  - desktop-locals-to-save. List of local variables to save.
+  - desktop-globals-to-clear. List of global variables that `desktop-clear' will clear.
+  - desktop-clear-preserve-buffers-regexp. Regexp identifying buffers that `desktop-clear'
+    should not delete.
+  - desktop-restore-eager. Number of buffers to restore immediately. Remaining buffers are
+    restored lazily (when Emacs is idle).
+  - desktop-lazy-verbose. Verbose reporting of lazily created buffers.
+  - desktop-lazy-idle-delay. Idle delay before starting to create buffers.
 *** New command line option --no-desktop