add nvchad_theme global in options.lua

lua/core/options.lua

@@ -1,6 +1,8 @@
 local opt = vim.opt
 local g = vim.g
 
+g.nvchad_theme = nvchad.load_config().ui.theme
+
 -- use filetype.lua instead of filetype.vim
 g.did_load_filetypes = 0
 g.do_filetype_lua = 1