add keybpard navigation for listviews
Summary:
when the main item of a scrollablepage is a listview, use
arrows to navigate
Test Plan: works fine in the gallery
Reviewers: Kirigami, apol
Reviewed By: apol
Subscribers: apol, plasma-devel
Tags: Kirigami
Differential Revision: https://phabricator.kde.org/D3793