patch 8.2.2813: cannot grep using fuzzy matching

Problem:    Cannot grep using fuzzy matching.
Solution:   Add the "f" flag to :vimgrep. (Yegappan Lakshmanan, closes #8152)
diff --git a/runtime/doc/quickfix.txt b/runtime/doc/quickfix.txt
index 2f34f49..ae29987 100644
--- a/runtime/doc/quickfix.txt
+++ b/runtime/doc/quickfix.txt
@@ -1008,7 +1008,7 @@
 5.1 using Vim's internal grep
 
 					*:vim* *:vimgrep* *E682* *E683*
-:vim[grep][!] /{pattern}/[g][j] {file} ...
+:vim[grep][!] /{pattern}/[g][j][f] {file} ...
 			Search for {pattern} in the files {file} ... and set
 			the error list to the matches.  Files matching
 			'wildignore' are ignored; files in 'suffixes' are
@@ -1059,20 +1059,20 @@
 				:vimgrep Error *.c
 <
 							*:lv* *:lvimgrep*
-:lv[imgrep][!] /{pattern}/[g][j] {file} ...
+:lv[imgrep][!] /{pattern}/[g][j][f] {file} ...
 :lv[imgrep][!] {pattern} {file} ...
 			Same as ":vimgrep", except the location list for the
 			current window is used instead of the quickfix list.
 
 						*:vimgrepa* *:vimgrepadd*
-:vimgrepa[dd][!] /{pattern}/[g][j] {file} ...
+:vimgrepa[dd][!] /{pattern}/[g][j][f] {file} ...
 :vimgrepa[dd][!] {pattern} {file} ...
 			Just like ":vimgrep", but instead of making a new list
 			of errors the matches are appended to the current
 			list.
 
 						*:lvimgrepa* *:lvimgrepadd*
-:lvimgrepa[dd][!] /{pattern}/[g][j] {file} ...
+:lvimgrepa[dd][!] /{pattern}/[g][j][f] {file} ...
 :lvimgrepa[dd][!] {pattern} {file} ...
 			Same as ":vimgrepadd", except the location list for
 			the current window is used instead of the quickfix