Add markdown rendering to Neovim with render-markdown.nvim

- Add render-markdown plugin for in-buffer markdown preview
- Add <leader>md keybinding to toggle markdown rendering
- Update README documentation with markdown rendering features
- Uses existing treesitter and web-devicons dependencies

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -47,6 +47,7 @@ home-manager switch --flake github:Logan-Lin/nix-config#yanlin
 - **Git Integration**: vim-fugitive for git operations
 - **Status Line**: lualine with gruvbox theme and relative paths
 - **System Clipboard**: Seamless integration for copy/paste
+- **Markdown Rendering**: render-markdown.nvim for beautiful in-buffer markdown preview
 
 #### Keybindings:
 
@@ -63,6 +64,7 @@ home-manager switch --flake github:Logan-Lin/nix-config#yanlin
 | `<Space>gd` | Normal | Git diff |
 | `<Space>gc` | Normal | Git commit |
 | `<Space>gp` | Normal | Git push |
+| `<Space>md` | Normal | Toggle markdown rendering |
 
 ### 🖥️ Tmux
 

nvim.nix

@@ -81,6 +81,11 @@
       web-devicons = {
         enable = true;
       };
+
+      # Markdown rendering
+      render-markdown = {
+        enable = true;
+      };
     };
 
     # Extra plugins that don't have dedicated modules
@@ -171,6 +176,14 @@
         action = ":Git push<CR>";
         options = { desc = "Git push"; };
       }
+
+      # Markdown rendering
+      {
+        mode = "n";
+        key = "<leader>md";
+        action = ":RenderMarkdown toggle<CR>";
+        options = { desc = "Toggle markdown rendering"; };
+      }
     ];
 
     # Additional Lua configuration for plugins that need custom setup