should disable xkbswitch on macOS for statusline

[jdhao]

If xkbswitch is not available, then just diable it on statusline.

[jdhao]

diff --git i/lua/plugins.lua w/lua/plugins.lua
index 078e1eb..1171295 100644
--- i/lua/plugins.lua
+++ w/lua/plugins.lua
@@ -222,7 +222,7 @@ packer.startup {

     use { "nvim-zh/better-escape.vim", event = { "InsertEnter" } }

-    if vim.g.is_mac then
+    if vim.g.is_mac and utils.executable('xkbswitch') then
       use { "lyokha/vim-xkbswitch", event = { "InsertEnter" } }
     elseif vim.g.is_win then
       use { "Neur1n/neuims", event = { "InsertEnter" } }