Add :Chmod command to change mode bits

lua/commands.lua

@@ -99,7 +99,13 @@ end, {
   end
 })
 
--- TODO: :Chmod
+-- :Chmod change file mode bits
+if vim.fn.executable('chmod') == 1 then
+  vim.api.nvim_create_user_command('Chmod', function(opts)
+    local file = vim.fn.expand('%:p')
+    vim.fn.system('chmod ' .. opts.args .. ' ' .. file)
+  end, { nargs = '+' })
+end
 
 -- :Mkdir create a directory, bang to create intermediate directories
 vim.api.nvim_create_user_command('Mkdir', function(opts)