Use plasma TextArea for sharing text in plasmoid
Summary:
This also fixes a bug where the box could be too small.
BUG: 400862
Reviewers: KDE Connect, nicolasfella
Reviewed By: KDE Connect, nicolasfella
Subscribers: nicolasfella, sredman, apol, kdeconnect
Tags: KDE Connect
Differential Revision: https://phabricator.kde.org/D16782