(Website) Cannot generate completions for bash and zsh without sudo

On the [website](https://usage.jdx.dev/cli/completions) the instructions for generating completions for bash and zsh are given as:
```bash
usage --completions bash > /etc/bash_completion.d/usage
usage --completions zsh > /usr/share/zsh/site-functions/_usage
```

The problem is redirection to those directories requires root access so both commands would fail. Here is the improved version using 'tee' with 'sudo':
```bash
usage --completions bash | sudo tee /etc/bash_completion.d/usage
usage --completions zsh | sudo tee /usr/share/zsh/site-functions/_usage
```
If echoing the content of completions to stdout is undesirable, it can be hidden:
```bash
usage --completions bash | sudo tee /etc/bash_completion.d/usage >/dev/null
usage --completions zsh | sudo tee /usr/share/zsh/site-functions/_usage >/dev/null
```