runtime(lf): improve syntax script, add filetype plugin

- Greatly improve detection and highlighting of command/shell regions,
  input-device key labels, escape sequences (@joelim-work)
- Add ftplugin for formatoptions, toggling comment areas
  (@andis-sprinkis)
- Add a few missing lf option keywords, rm. old non-working code, misc.
  formatting (@andis-sprinkis)

closes: #17078

Signed-off-by: Andis Spriņķis <andis@sprinkis.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/ftplugin/lf.vim

@@ -0,0 +1,22 @@
+" Vim filetype plugin file
+" Language: lf file manager configuration file (lfrc)
+" Maintainer: Andis Sprinkis <andis@sprinkis.com>
+" URL: https://github.com/andis-sprinkis/lf-vim
+" Last Change: 6 Apr 2025
+
+if exists("b:did_ftplugin") | finish | endif
+
+let b:did_ftplugin = 1
+
+let s:cpo = &cpo
+set cpo&vim
+
+let b:undo_ftplugin = "setlocal comments< commentstring< formatoptions<"
+
+setlocal comments=:#
+setlocal commentstring=#\ %s
+
+setlocal formatoptions-=t formatoptions+=rol
+
+let &cpo = s:cpo
+unlet s:cpo