Add Telegram plugin

Summary: Add a "Share via Telegram plugin". It's a copy of the KDE Connect plugin with name/command substituted. Telegram expects the path without file:// prefix so it is removed when found.

Test Plan:
Share from Okular works.
Share from Spectacle does not work since Spectacle does not give an URL but the image data.

Reviewers: apol

Reviewed By: apol

Subscribers: ngraham, kde-frameworks-devel, apol

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D12896