add ability to just print magnet links or just download .torrent files

currently using this on a windows system, I tried using WSL

I don't want to use the libtorrent client, I'd like to use anything else of my choosing like qbittorrent (since I use it for other websites)

qbittorrent does support piping magnet link strings to it and I've done it before, but nyaa-cli doesn't have this option of printing the magnet links

I'll look into it and might submit a pull request if I get something working, but leaving this here for now

one suggestion is to change the `--client` flag from a bool to a parameter where you can specify which client to use

Start by locating the CLI handling for the `--client` flag and the existing torrent-download path. The change is done when users can print magnet links or download `.torrent` files without requiring libtorrent, with support for choosing another client such as qBittorrent.

Written by the indexing model from the issue text.