Add NvChadUpdate command and shortcut for it

map leader+uu to it

summary of what it does:

first ask the user for confirmation and tell that the updater is gonna run git reset --hard in config repo and chadrc will be restored

take backup of chadrc in a lua string and locally in a file with chadrc.bak.(random numbers)

git reset on config dir and git pull

whether success or error, restore the chadrc file

if restore fails, then print backup file path

for more deep understanding, read the comments in utils.lua

lua/chadrc.lua

@@ -141,6 +141,7 @@ M.mappings = {
       copywhole_file = "<C-a>",
       toggle_linenr = "<leader>n", -- show or hide line number
       theme_toggle = "<leader>x",
+      update_nvchad = "<leader>uu",
    },
 }