Add "SkipSwitcher" to API

Summary:
Adding "SkipSwitcher" to API, as a result of discussion in
BUG 375921

Depends on / related to D11924 and D11926.

Reviewers: hein, graesslin

Reviewed By: graesslin

Subscribers: kde-frameworks-devel, lbeltrame, rikmills, davidedmundson, #plasma, graesslin

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D11925