Add `iTransmission` to Community Source

[Alexs1987]

About

iTransmission is a fast, easy and Free Bittorrent Client for iOS 13+
It is based on the awesome Transmission library.
It contains many features such as background download, built-in browser, file app support and much more.

Link

Repo: https://github.com/alexsvitlov/iTransmission

Release Page: https://github.com/alexsvitlov/iTransmission/releases