Add --imgbox and --imginputbox support for KDialog

Summary:
I have added 2 new options for Image Box and Image Input Box in KDialog because I did not find any.

Here is how they look.

{F6518950}

{F6518951}

Reviewers: #kdialog, dfaure

Reviewed By: #kdialog, dfaure

Subscribers: dfaure, #kdialog

Tags: #kdialog

Differential Revision: https://phabricator.kde.org/D17895