[handler] Embed URL into string

Summary:
E.g.
Device to call +1234567 with
Device to send /home/nico/foo to
Device to open http://google.com on

Reviewers: KDE Connect, apol

Reviewed By: KDE Connect, apol

Subscribers: apol, kdeconnect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D16623