patch 9.1.0778: filetype: lf config files are not recognized

Problem:  filetype: lf config files are not recognized
Solution: detect lfrc files as lf filetype, include a syntax
          script for lf files (Andis Spriņķis).

References:
- https://github.com/gokcehan/lf

closes: #15859

Signed-off-by: Andis Spriņķis <spr.andis@protonmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 6b7dbf9..29bb7b5 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2024 Oct 06
+*syntax.txt*	For Vim version 9.1.  Last change: 2024 Oct 13
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2223,6 +2223,20 @@
 	:let lace_case_insensitive=1
 
 
+LF (LFRC)		*lf.vim* *ft-lf-syntax* *g:lf_shell_syntax*
+						*b:lf_shell_syntax*
+
+For the lf file manager configuration files (lfrc) the shell commands
+syntax highlighting can be changed globally and per buffer by setting
+a different 'include' command search pattern using these variables:
+	let g:lf_shell_syntax = "syntax/dosbatch.vim"
+	let b:lf_shell_syntax = "syntax/zsh.vim"
+
+These variables are unset by default.
+
+The default 'include' command search pattern is 'syntax/sh.vim'.
+
+
 LEX						*lex.vim* *ft-lex-syntax*
 
 Lex uses brute-force synchronizing as the "^%%$" section delimiter