ward completions -- Please don't write to .zshrc by default

[AndydeCleyre]

Hello!

I have three problems with what happens when running ward completions:

1. Please don't alter my precious dotfiles without some kind of explicit request or confirmation
2. ~/.zshrc isn't even the correct path in many cases (like mine). I have ZDOTDIR set to ~/.config/zsh.
3. The completions don't seem to work, either. Neither when sourcing the produced output nor dropping it as a file in one of the user's fpath folders.

Here are some contrasting examples of how I install completions for other tools providing a completions subcommand:

$ mise completion zsh >~/.local/share/zsh/site-packages/_mise
$ ruff generate-shell-completion zsh >~/.local/share/zsh/site-packages/_ruff
$ uv generate-shell-completion zsh >~/.local/share/zsh/site-packages/_uv
$ prqlc shell-completion zsh >~/.local/share/zsh/site-packages/_prqlc
$ pip completion -z $ZDOTDIR/plugins/pip.zsh  # and add `. $ZDOTDIR/plugins/pip.zsh` to my `.zshrc`