vim-patch:9.2.0786: filetype: Containerfile is not recognized (#40807)

Problem:  filetype: Containerfile is not recognized
Solution: Detect *.[Cc]ontainerfiles as dockerfile filetype
          (Omer Tuchfeld)

closes: vim/vim#20783

Supported by AI.

6b62ae68c6

Co-authored-by: Omer Tuchfeld <omer@tuchfeld.dev>

runtime/lua/vim/filetype.lua

@@ -444,6 +444,8 @@ local extension = {
   rej = 'diff',
   dj = 'djot',
   djot = 'djot',
+  Containerfile = 'dockerfile',
+  containerfile = 'dockerfile',
   Dockerfile = 'dockerfile',
   dockerfile = 'dockerfile',
   bat = 'dosbatch',