New Extractor Idea: `aria2` with bittorrents link/FTP/SFTP/Metalink download support

https://github.com/aria2/aria2

Would behave similarly to the wget extractor.

We should also consider extractors for:

- `rsync`
- `rclone`
- `icloudpd` https://github.com/icloud-photos-downloader/icloud_photos_downloader
- `zfs recv`
- `ssh <arbitrarycommand>`
- `lftp` https://github.com/lavv17/lftp