patch 8.2.2675: directory change in a terminal window shell is not followed

Problem:    Directory change in a terminal window shell is not followed.
Solution:   Add the 'autoshelldir' option. (closes #6290)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 7fcdfbe..babe721 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -749,6 +749,15 @@
 	or selected.
 	Note: When this option is on some plugins may not work.
 
+			*'autoshelldir'* *'asd'* *'noautoshelldir'* *'noasd'*
+'autoshelldir' 'asd'	boolean (default off)
+			global
+	When on, Vim will change the current working directory whenever you
+	change the directory of the shell running in a terminal window. You
+	need proper setting-up, so whenever the shell's pwd changes an OSC 7
+	escape sequence will be emitted. For example, on Linux, you can source
+	/etc/profile.d/vte.sh in your shell profile if you use bash or zsh.
+
 				*'arabic'* *'arab'* *'noarabic'* *'noarab'*
 'arabic' 'arab'		boolean (default off)
 			local to window