vim-patch:9.1.2043: filetype: kos files are not reconized

Problem:  filetype: kos files are not reconized
Solution: Detect *.kos files as kos filetype
          (Chris Dragan)

Reference:
- https://github.com/kos-lang/kos

closes: vim/vim#19056

96a1caac6b

Co-authored-by: Chris Dragan <chris@dragan.dev>

runtime/lua/vim/filetype.lua

@@ -691,6 +691,7 @@ local extension = {
   kerml = 'kerml',
   kv = 'kivy',
   kix = 'kix',
+  kos = 'kos',
   kts = 'kotlin',
   kt = 'kotlin',
   ktm = 'kotlin',