patch 8.2.3780: ":cd" works differently on MS-Windows

Problem:    ":cd" works differently on MS-Windows.
Solution:   Add the 'cdhome' option. (closes #9324)
diff --git a/runtime/doc/quickref.txt b/runtime/doc/quickref.txt
index f1e2ac4..aa5a36a 100644
--- a/runtime/doc/quickref.txt
+++ b/runtime/doc/quickref.txt
@@ -635,6 +635,7 @@
 'buflisted'	  'bl'	    whether the buffer shows up in the buffer list
 'buftype'	  'bt'	    special type of buffer
 'casemap'	  'cmp'     specifies how case of letters is changed
+'cdhome'	  'cdh'	    change directory to the home directory by ":cd"
 'cdpath'	  'cd'	    list of directories searched with ":cd"
 'cedit'			    key used to open the command-line window
 'charconvert'	  'ccv'     expression for character encoding conversion