Add zsh-autosuggestions and zsh-syntax-highlighting as git submodules

- Added both plugins as git submodules in zsh/custom-plugins/
- Created symlinks in oh-my-zsh custom plugins directory
- Plugins are now properly managed and will work with the existing oh-my-zsh setup

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

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

.gitmodules

@@ -4,3 +4,9 @@
 [submodule "zsh/oh-my-zsh"]
 	path = zsh/oh-my-zsh
 	url = https://github.com/ohmyzsh/ohmyzsh.git
+[submodule "zsh/custom-plugins/zsh-autosuggestions"]
+	path = zsh/custom-plugins/zsh-autosuggestions
+	url = https://github.com/zsh-users/zsh-autosuggestions
+[submodule "zsh/custom-plugins/zsh-syntax-highlighting"]
+	path = zsh/custom-plugins/zsh-syntax-highlighting
+	url = https://github.com/zsh-users/zsh-syntax-highlighting