docs(v3.5.0): update README for integrated mg_dotfiles and security improvements

- Integrated mg_dotfiles as regular directory (not submodule)
- Added .zshrc.local.example template for local configs without secrets
- Added mg_dotfiles/zsh/.zshrc.local to .gitignore to protect API keys
- Updated README to reflect mg_dotfiles integration and new structure
- Added nvim configuration directory with LazyVim setup

mg_dotfiles/nvim/lua/plugins/vim-be-good.lua

@@ -0,0 +1,8 @@
+-- This file contains the configuration for the vim-be-good plugin in Neovim.
+
+return {
+  -- Plugin: vim-be-good
+  -- URL: https://github.com/ThePrimeagen/vim-be-good
+  -- Description: A Neovim plugin designed to help you improve your Vim skills through various exercises and games.
+  "ThePrimeagen/vim-be-good",
+}