patch 9.1.1042: filetype: just files are not recognized

Problem:  filetype: just files are not recognized
Solution: adjust filetype detection pattern, detect just shebang line,
          include just ftplugin, indent and syntax plugin
          (Peter Benjamin)

closes: #16466

Signed-off-by: Peter Benjamin <petermbenjamin@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/autoload/dist/script.vim

@@ -4,7 +4,7 @@ vim9script
 # Invoked from "scripts.vim" in 'runtimepath'
 #
 # Maintainer:	The Vim Project <https://github.com/vim/vim>
-# Last Change:	2023 Aug 10
+# Last Change:	2025 Jan 20
 # Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 export def DetectFiletype()
@@ -133,6 +133,9 @@ export def Exe2filetype(name: string, line1: string): string
   elseif name =~ 'node\(js\)\=\>\|js\>' || name =~ 'rhino\>'
     return 'javascript'
 
+  elseif name =~# 'just'
+    return 'just'
+
     # BC calculator
   elseif name =~ '^bc\>'
     return 'bc'