vim-patch:9.1.0906: filetype: Nvidia PTX files are not recognized

Problem:  filetype: Nvidia PTX files are not recognized
Solution: detect '*.ptx' files as ptx filetype (Yinzuo Jiang)

Reference: https://docs.nvidia.com/cuda/parallel-thread-execution/

closes: vim/vim#16171

bdb5f85a51

Co-authored-by: Yinzuo Jiang <jiangyinzuo@foxmail.com>

runtime/lua/vim/filetype.lua

@@ -958,6 +958,7 @@ local extension = {
   ps1xml = 'ps1xml',
   psf = 'psf',
   psl = 'psl',
+  ptx = 'ptx',
   pug = 'pug',
   purs = 'purescript',
   arr = 'pyret',