D5111: Provide demo/preview for checkable menu items and colour scheme comparison

[René J . V . Bertin]

rjvbb set the repository for this revision to R113 Oxygen Theme.

REPOSITORY
  R113 Oxygen Theme

REVISION DETAIL
  https://phabricator.kde.org/D5111

To: rjvbb, jriddell, anthonyfieroni, zhigalin, hpereiradacosta
Cc: ltoscano, kde-mac, #frameworks