vim-patch:9.1.0010: Keymap completion is not available (#26888)

Problem:  Keymap completion is not available
Solution: Add keymap completion (Doug Kearns)

Add keymap completion to the 'keymap' option, user commands and builtin
completion functions.

closes: vim/vim#13692

81642d9d6f

Co-authored-by: Doug Kearns <dougkearns@gmail.com>

src/nvim/usercmd.c

@@ -75,6 +75,7 @@ static const char *command_complete[] = {
   [EXPAND_HELP] = "help",
   [EXPAND_HIGHLIGHT] = "highlight",
   [EXPAND_HISTORY] = "history",
+  [EXPAND_KEYMAP] = "keymap",
 #ifdef HAVE_WORKING_LIBINTL
   [EXPAND_LOCALES] = "locale",
 #endif