Added a new Telegram module, which allows to send a message via Telegram
using the Telegram Bot API. The commit also includes:
- Update for the Telegram returner (merged in #44148); the Telegram
returner now fully utilizes the Telegram module.
- Update to the documentation in order to add the Telegram module to the
list list of all modules.
- Updated Telegram returner test.
- New Telegram module test.
