New function insert-special-event and special event sleep-event

New function insert-special-event and special event sleep-event

* doc/lispref/commands.texi (Misc Events): Add sleep-event.
(Special Events): New function insert-special-event.

* etc/NEWS: New function insert-special-event.  New event 'sleep-event'.
Fix typos.

* src/keyboard.c (Finsert_special_event): New defun.
(syms_of_keyboard): Declare Qsleep_event.  Define subroutine
Sinsert_special_event.  Add sleep-event to Vspecial_event_map.
(Bug#63620)
(kbd_buffer_get_event, make_lispy_event)
(init_while_no_input_ignore_events, is_ignored_event):
* src/termhooks.h (event_kind): Add SLEEP_EVENT.

(cherry picked from commit d41178368eb73873f34c15b58062a7447802c914)