Add Zoom scroll wheel option

Summary:
Adding a Zoom option for scrolling in the configuration

BUG: 254511
FIXED-IN: 18.12.0

Test Plan: Test scrolling in image and folder view for each configuration selection.

Reviewers: #gwenview, ngraham

Reviewed By: ngraham

Subscribers: sourabhboss, muhlenpfordt, ngraham

Tags: #gwenview

Differential Revision: https://phabricator.kde.org/D15809