Add TR4KER search plugin details to mediawiki

[Apologieze]

Add unofficial tr4ker.net qBittorrent search plugin entry

Summary

This PR adds an unofficial qBittorrent search plugin entry for tr4ker.net to the Unofficial-search-plugins wiki page under Plugins for Private Sites.

Details

• The plugin is maintained externally by Apologieze
• It uses the native tr4ker.net Torznab API
• It requires a user-provided API key and local configuration
• It does not embed any personal credentials or secrets

Repository

• Plugin repository: https://github.com/Apologieze/qbittorrent-tr4ket-plugin
• Direct download URL: https://raw.githubusercontent.com/Apologieze/qbittorrent-tr4ket-plugin/refs/heads/main/tr4ker.py

Notes

This plugin targets a semi-private tracker, so the unofficial plugins wiki seemed like the appropriate place to publish it.