patch 9.1.0207: No autocommand when writing session file

Problem:  No autocommand when writing session file
Solution: Add SessionWritePost autocommand
          (Colin Kennedy)

fixes: ##14242
closes: #14288

Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Colin Kennedy <colinvfx@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/autocmd.txt b/runtime/doc/autocmd.txt
index 5f9f51e..32094b3 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -1,4 +1,4 @@
-*autocmd.txt*   For Vim version 9.1.  Last change: 2024 Jan 25
+*autocmd.txt*   For Vim version 9.1.  Last change: 2024 Mar 26
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -428,6 +428,9 @@
 
 |SessionLoadPost|	after loading a session file
 
+|SessionWritePost|	After writing the session file using
+			the |:mksession| command.
+
 |MenuPopup|		just before showing the popup menu
 |CompleteChanged|	after Insert mode completion menu changed
 |CompleteDonePre|	after Insert mode completion is done, before clearing
@@ -1115,6 +1118,9 @@
 							*SessionLoadPost*
 SessionLoadPost			After loading the session file created using
 				the |:mksession| command.
+							*SessionWritePost*
+SessionWritePost		After writing a session file by calling
+				the |:mksession| command.
 							*ShellCmdPost*
 ShellCmdPost			After executing a shell command with |:!cmd|,
 				|:shell|, |:make| and |:grep|.  Can be used to