[SMS App] Allow passing a message via args

Summary:
Add --message option to kdeconnect-sms to pass a message. The user only needs to choose a recepient and the message will be sent. Useful for integration with 3rd party
apps, e.g. via Purpose

Test Plan:
kdeconnect-sms --message "Hello World", choose chat, message is sent
Click another chat, no message sent
kdeconnect-sms without args, no message sent

Reviewers: KDE Connect, sredman

Reviewed By: KDE Connect, sredman

Subscribers: andyholmes, sredman, apol, kdeconnect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D17292