Add "SkipSwitcher" to API

Summary:
Adding "SkipSwitcher" to the API, following discussion in
BUG 375921

Depends on / related to D11925 and D11924

Reviewers: hein, #kwin, graesslin

Reviewed By: #kwin, graesslin

Subscribers: davidedmundson, #plasma, ngraham, kwin, #kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D11926