vim-patch:9.0.1106: not all postfix files are recognized (#21568)

Problem:    Not all postfix files are recognized.
Solution:   Recognize main.cf.proto files. (closes vim/vim#11732)

09ce0b8e11

Co-authored-by: KodeToad <3880336+KodeToad@users.noreply.github.com>

runtime/lua/vim/filetype.lua

@@ -1532,6 +1532,7 @@ local filename = {
   ['.latexmkrc'] = 'perl',
   ['pf.conf'] = 'pf',
   ['main.cf'] = 'pfmain',
+  ['main.cf.proto'] = 'pfmain',
   pinerc = 'pine',
   ['.pinercex'] = 'pine',
   ['.pinerc'] = 'pine',