patch 9.1.0464: no whitespace padding in commentstring option in ftplugins

Problem:  no whitespace padding in commentstring option in ftplugins
Solution: Change default to include whitespace padding, update
          existing filetype plugins with the new default value
          (Riley Bruins)

closes: #14843

Signed-off-by: Riley Bruins <ribru17@hotmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/ftplugin/markdown.vim b/runtime/ftplugin/markdown.vim
index 022dd0d..d4ee5ac 100644
--- a/runtime/ftplugin/markdown.vim
+++ b/runtime/ftplugin/markdown.vim
@@ -2,6 +2,7 @@
 " Language:     Markdown
 " Maintainer:   Tim Pope <https://github.com/tpope/vim-markdown>
 " Last Change:  2023 Dec 28
+"               2024 May 24 by Riley Bruins <ribru17@gmail.com> ('commentstring')
 
 if exists("b:did_ftplugin")
   finish
@@ -12,7 +13,7 @@
 let s:keepcpo= &cpo
 set cpo&vim
 
-setlocal comments=fb:*,fb:-,fb:+,n:> commentstring=<!--%s-->
+setlocal comments=fb:*,fb:-,fb:+,n:> commentstring=<!--\ %s\ -->
 setlocal formatoptions+=tcqln formatoptions-=r formatoptions-=o
 setlocal formatlistpat=^\\s*\\d\\+\\.\\s\\+\\\|^\\s*[-*+]\\s\\+\\\|^\\[^\\ze[^\\]]\\+\\]:\\&^.\\{4\\}