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)

runtime/doc/options.txt

@@ -749,6 +749,15 @@ A jump table for the options with a short description can be found at |Q_op|.
 	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

runtime/doc/quickref.txt

@@ -605,6 +605,7 @@ Short explanation of each option:		*option-list*
 'ambiwidth'	  'ambw'    what to do with Unicode chars of ambiguous width
 'antialias'	  'anti'    Mac OS X: use smooth, antialiased fonts
 'autochdir'	  'acd'     change directory to the file in the current window
+'autoshelldir'	  'asd'     change directory to the shell's current directory
 'arabic'	  'arab'    for Arabic as a default second language
 'arabicshape'	  'arshape' do shaping for Arabic characters
 'autoindent'	  'ai'	    take indent for new line from previous line