Introduce the use of `clap_completion` for generating static completion.
The shells that are supported are the ones that are included in `clap_complete`:
- `bash`,
- `elvish`,
- `zsh`,
- `fish`, and
- `powershell`.
Co-authored-by: Michael Uti <utimichael9@gmail.com>
Co-authored-by: Lorenz Leutgeb <lorenz.leutgeb@radicle.xyz>