Add auto-completion for zsh

Switch between your git worktrees even faster! ⚡ Now with tab autocompletion for both Bash and ZSH! ✨

Enable Tab Autocompletion: 🚀
https://github.com/yankeexe/git-worktree-switcher#tab-autocompletion-zap

• bash: wt_completion
• zsh: _wt_completion