Summary:
Adds a tooltip to the configure panel button.
{F6556503}

Test Plan: Hover over the configure panel button

Reviewers: #plasma, #vdg, ndavis, ngraham

Reviewed By: #vdg, ndavis, ngraham

Subscribers: Codezela, ngraham, ndavis, #vdg, plasma-devel, #plasma

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D18381