Summary:
Use bigtext style.

BUG: 402489

Test Plan: Send notification with long text. Before a single line was shown. Now the user can view the full content by pulling down the notification

Reviewers: #kde_connect, albertvaka

Reviewed By: #kde_connect, albertvaka

Subscribers: kdeconnect

Tags: #kde_connect

Differential Revision: https://phabricator.kde.org/D17786