runtime(help): Add better support for language annotation highlighting

closes: #16238

Co-authored-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: h_east <h.east.727@gmail.com>
Signed-off-by: Shougo Matsushita <Shougo.Matsu@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/help.vim b/runtime/syntax/help.vim
index 3886164..ec5739f 100644
--- a/runtime/syntax/help.vim
+++ b/runtime/syntax/help.vim
@@ -1,7 +1,7 @@
 " Vim syntax file
 " Language:	Vim help file
 " Maintainer:	The Vim Project <https://github.com/vim/vim>
-" Last Change:	2024 Dec 15
+" Last Change:	2024 Dec 25
 " Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 " Quit when a (custom) syntax file was already loaded
@@ -12,26 +12,36 @@
 let s:cpo_save = &cpo
 set cpo&vim
 
+if !exists('g:help_example_languages')
+  let g:help_example_languages = #{ vim: 'vim' }
+endif
+
 syn match helpHeadline		"^[A-Z.][-A-Z0-9 .,()_']*?\=\ze\(\s\+\*\|$\)"
 syn match helpSectionDelim	"^===.*===$"
 syn match helpSectionDelim	"^---.*--$"
 
-unlet! b:current_syntax
-" sil! to prevent E403
-silent! syntax include @VimScript syntax/vim.vim
 if has("conceal")
-  syn region helpExample	matchgroup=helpIgnore start=" >$" start="^>$" end="^[^ \t]"me=e-1 end="^<" concealends
-  syn region helpExampleVimScript matchgroup=helpIgnore
-        \ start=/^>vim$/ start=/ >vim$/
-        \ end=/^[^ \t]/me=e-1 end=/^</ concealends
-        \ contains=@VimScript keepend
+  syn region helpExample	matchgroup=helpIgnore
+        \ start="\%(^\| \)>[a-z0-9]*$" end="^[^ \t]"me=e-1 end="^<" concealends
  else
-   syn region helpExample	matchgroup=helpIgnore start=" >$" start="^>$" end="^[^ \t]"me=e-1 end="^<"
-   syn region helpExampleVimScript matchgroup=helpIgnore
-         \ start=/^>vim$/ start=/ >vim$/
-         \ end=/^[^ \t]/me=e-1 end=/^</
-         \ contains=@VimScript keepend
+   syn region helpExample	matchgroup=helpIgnore
+         \ start="\%(^\| \)>[a-z0-9]*$" end="^[^ \t]"me=e-1 end="^<"
 endif
+
+for [s:lang, s:syntax] in g:help_example_languages->items()
+  unlet! b:current_syntax
+  " silent! to prevent E403
+  execute 'silent! syn include' $'@helpExampleHighlight_{s:lang}'
+        \ $'syntax/{s:syntax}.vim'
+
+  execute $'syn region helpExampleHighlight_{s:lang} matchgroup=helpIgnore'
+        \ $'start=/\%(^\| \)>{s:lang}$/'
+        \ 'end=/^[^ \t]/me=e-1 end=/^</'
+        \ (has("conceal") ? 'concealends' : '')
+        \ $'contains=@helpExampleHighlight_{s:lang} keepend'
+endfor
+unlet! s:lang s:syntax
+
 if has("ebcdic")
   syn match helpHyperTextJump	"\\\@<!|[^"*|]\+|" contains=helpBar
   syn match helpHyperTextEntry	"\*[^"*|]\+\*\s"he=e-1 contains=helpStar