[Feature]: Subscribe to channels besides Youtube

Prerequisites

• I have searched existing issues and discussions to ensure this feature hasn't been requested before
• I have read the feature request guidelines in the README
• I understand that MeTube development relies on community contributions and the maintainer is not likely to implement this feature
• I have considered if this feature should be implemented in yt-dlp instead of MeTube (if so, please report to yt-dlp repository)

Feature Description

Metube has the capabilities of downloading full channels and playlists from YouTube. It also allows up to subscribe to same channels and playlists if we want to. Pornhub also allows downloading full channels and playlists but it's unable to process subscribed ones. Could that option be added? Thanks in advance.

Implementation Plan

None

Additional Context

No response