vim-patch:9.0.2098: No filetype support for xcompose files (#25983)

Problem:  No filetype support for xcompose files
Solution: Add filetype detection

closes: vim/vim#13508

4f9074b96c

runtime/lua/vim/filetype.lua

@@ -1521,6 +1521,8 @@ local filename = {
   wget2rc = 'wget2',
   ['.wvdialrc'] = 'wvdial',
   ['wvdial.conf'] = 'wvdial',
+  ['.XCompose'] = 'xcompose',
+  ['Compose'] = 'xcompose',
   ['.Xresources'] = 'xdefaults',
   ['.Xpdefaults'] = 'xdefaults',
   ['xdm-config'] = 'xdefaults',