D17190: Add level api from Kirigami.Heading

[Fabian Riethmayer]

fabianr edited the summary of this revision.

REPOSITORY
  R236 KWidgetsAddons

REVISION DETAIL
  https://phabricator.kde.org/D17190

To: mart, #plasma, #vdg
Cc: ngraham, kde-frameworks-devel, michaelh, bruns