Fix Kirigami template image
Summary: Kirigami template image file is empty. An image file that shows a Kirigami application was added.
Test Plan: Try to create a Kirigami application with kdevelop or kapptemplate, using the template found in Qt > Graphical > Kirigami Application; an image is shown, showing how the application will look like.
Reviewers: apol, ngraham, mart
Reviewed By: apol, ngraham, mart
Differential Revision: https://phabricator.kde.org/D24674