my edit so far

lua/custom/plugins/init.lua

@@ -2,4 +2,8 @@
 --  I promise not to create any merge conflicts in this directory :)
 --
 -- See the kickstart.nvim README for more information
-return {}
+return {
+  { 'CRAG666/code_runner.nvim', config = true },
+  { 'mbbill/undotree' },
+  vim.keymap.set('n', '<leader><F5>', vim.cmd.UndotreeToggle, { desc = 'UndoTree' }),
+}