runtime(nu): Add new Nushell runtime files

See: https://github.com/elkasztano/nushell-syntax-vim

Thanks to Pete Cruz (@Petesta) for promoting this addition.

closes: #18208

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/ftplugin/nu.vim

@@ -1,13 +1,17 @@
 " Vim filetype plugin
-" Language:	Nu
-" Maintainer:	Marc Jakobi <marc@jakobi.dev>
-" Last Change:	2024 Aug 31
+" Language:	Nushell
+" Maintainer:	El Kasztano
+" URL:		https://github.com/elkasztano/nushell-syntax-vim
+" License:	MIT <https://opensource.org/license/mit>
+" Last Change:	2025 Sep 05
 
-if exists('b:did_ftplugin')
+if exists("b:did_ftplugin")
   finish
 endif
 let b:did_ftplugin = 1
 
 setlocal commentstring=#\ %s
+setlocal comments-=://
+setlocal formatoptions=tcroql
 
-let b:undo_ftplugin = 'setl com<'
+let b:undo_ftplugin = "setl fo< cms< com<"