net-p2p/tremotesf: add new port

Tremotesf is yet another, but modern (first-released in 2016) cross-platfom GUI
for Transmission daemon written in C++ and Qt.

Features include, but not necessarily limited to:
* View torrent list
* Sort torrents
* Filter torrents by name, status and trackers
* Start/stop/verify/remove torrents with multi-selection
* Add torrents from torrent files and magnet links
* Select which files to download when adding torrent
* Manage torrent files
* Add and remove torrent trackers
* View torrent peers
* Set torrent limits
* Change remote server settings
* View server statistics
* Multiple servers
* Supports HTTPS connection
* Can connect to servers with self-signed certificates (you need to add
  certificate to server settings)
* Client certificate authentication

WWW: https://github.com/equeim/tremotesf2/

PR:		274236