runtime(r): Update R runtime files and docs (#13757)

* Update R runtime files
- Fix indentation issue with ggplot().
- Setlocal autoindent in indent/r.vim.
- New syntax option: rmd_include_latex.
- Clear syn iskeyword to recognize _ as keyword.
- Document some options.
- remove the test has("patch-7.4.1142")
- Update changed date of doc files

Signed-off-by: Jakson Alves de Aquino <jalvesaq@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org

runtime/syntax/r.vim

@@ -5,7 +5,7 @@
 " 		      Tom Payne <tom@tompayne.org>
 " Contributor:        Johannes Ranke <jranke@uni-bremen.de>
 " Homepage:           https://github.com/jalvesaq/R-Vim-runtime
-" Last Change:	      Thu Nov 17, 2022  10:13PM
+" Last Change:	      Sun Dec 24, 2023  08:05AM
 " Filenames:	      *.R *.r *.Rhistory *.Rt
 "
 " NOTE: The highlighting of R functions might be defined in
@@ -26,11 +26,7 @@ if exists("b:current_syntax")
   finish
 endif
 
-if has("patch-7.4.1142")
-  syn iskeyword @,48-57,_,.
-else
-  setlocal iskeyword=@,48-57,_,.
-endif
+syn iskeyword @,48-57,_,.
 
 " The variables g:r_hl_roxygen and g:r_syn_minlines were renamed on April 8, 2017.
 if exists("g:r_hl_roxygen")