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/markdown.lua

@@ -0,0 +1,21 @@
+return {
+  "MeanderingProgrammer/render-markdown.nvim",
+  dependencies = { "nvim-treesitter/nvim-treesitter", "nvim-mini/mini.nvim" }, -- if you use the mini.nvim suite
+  ---@module 'render-markdown'
+  ---@type render.md.UserConfig
+  opts = {
+    heading = {
+      enabled = true,
+      sign = true,
+      style = "full",
+      icons = { "① ", "② ", "③ ", "④ ", "⑤ ", "⑥ " },
+      left_pad = 1,
+    },
+    bullet = {
+      enabled = true,
+      icons = { "●", "○", "◆", "◇" },
+      right_pad = 1,
+      highlight = "render-markdownBullet",
+    },
+  },
+}